udhcpc6: new applet. Not yet functional.

It builds. It sends Solicit packets. Not sure these packets are well-formed.
I have no server to test it against.

function                                             old     new   delta
udhcpc6_main                                           -    2426   +2426
d6_send_raw_packet                                     -     428    +428
d6_send_kernel_packet                                  -     274    +274
d6_recv_raw_packet                                     -     248    +248
send_d6_discover                                       -     177    +177
packed_usage                                       28795   28966    +171
d6_run_script                                          -     156    +156
send_d6_renew                                          -     140    +140
send_d6_release                                        -     126    +126
d6_recv_kernel_packet                                  -     116    +116
send_d6_select                                         -      95     +95
perform_d6_release                                     -      78     +78
d6_find_option                                         -      74     +74
init_d6_packet                                         -      54     +54
d6_copy_option                                         -      48     +48
d6_mcast_from_client_config_ifindex                    -      42     +42
d6_dump_packet                                         -      24     +24
static.FF02__1_2                                       -      16     +16
d6_store_blob                                          -      13     +13
applet_names                                        2432    2440      +8
applet_main                                         1412    1416      +4
applet_nameofs                                       706     708      +2
add_d6_client_options                                  -       1      +1
------------------------------------------------------------------------------
(add/remove: 21/0 grow/shrink: 4/0 up/down: 4721/0)          Total: 4721 bytes
   text	   data	    bss	    dec	    hex	filename
 879080	    493	   7584	 887157	  d8975	busybox_old
 884585	    497	   7584	 892666	  d9efa	busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

4 files changed, 1724 insertions, 0 deletions

diff --git a/networking/udhcp/d6_common.h b/networking/udhcp/d6_common.h
new file mode 100644
index 0000000..88afaf8
--- /dev/null
+++ b/networking/udhcp/d6_common.h
@@ -0,0 +1,118 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Copyright (C) 2011 Denys Vlasenko.
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+#ifndef UDHCP_D6_COMMON_H
+#define UDHCP_D6_COMMON_H 1
+
+#include <netinet/ip6.h>
+
+PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
+
+
+/*** DHCPv6 packet ***/
+
+/* DHCPv6 protocol. See RFC 3315 */
+#define D6_MSG_SOLICIT              1
+#define D6_MSG_ADVERTISE            2
+#define D6_MSG_REQUEST              3
+#define D6_MSG_CONFIRM              4
+#define D6_MSG_RENEW                5
+#define D6_MSG_REBIND               6
+#define D6_MSG_REPLY                7
+#define D6_MSG_RELEASE              8
+#define D6_MSG_DECLINE              9
+#define D6_MSG_RECONFIGURE         10
+#define D6_MSG_INFORMATION_REQUEST 11
+#define D6_MSG_RELAY_FORW          12
+#define D6_MSG_RELAY_REPL          13
+
+struct d6_packet {
+	union {
+		uint8_t d6_msg_type;
+		uint32_t d6_xid32;
+	} d6_u;
+	uint8_t d6_options[576 - sizeof(struct iphdr) - sizeof(struct udphdr) - 4
+			+ CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS];
+} PACKED;
+#define d6_msg_type d6_u.d6_msg_type
+#define d6_xid32    d6_u.d6_xid32
+
+struct ip6_udp_d6_packet {
+	struct ip6_hdr ip6;
+	struct udphdr udp;
+	struct d6_packet data;
+} PACKED;
+
+struct udp_d6_packet {
+	struct udphdr udp;
+	struct d6_packet data;
+} PACKED;
+
+/*** Options ***/
+
+struct d6_option {
+	uint8_t code;
+	uint8_t code_hi;
+	uint8_t len;
+	uint8_t len_hi;
+	uint8_t data[1];
+} PACKED;
+
+#define D6_OPT_CLIENTID       1
+#define D6_OPT_SERVERID       2
+#define D6_OPT_IA_NA          3
+#define D6_OPT_IA_TA          4
+#define D6_OPT_IAADDR         5
+#define D6_OPT_ORO            6
+#define D6_OPT_PREFERENCE     7
+#define D6_OPT_ELAPSED_TIME   8
+#define D6_OPT_RELAY_MSG      9
+#define D6_OPT_AUTH          11
+#define D6_OPT_UNICAST       12
+#define D6_OPT_STATUS_CODE   13
+#define D6_OPT_RAPID_COMMIT  14
+#define D6_OPT_USER_CLASS    15
+#define D6_OPT_VENDOR_CLASS  16
+#define D6_OPT_VENDOR_OPTS   17
+#define D6_OPT_INTERFACE_ID  18
+#define D6_OPT_RECONF_MSG    19
+#define D6_OPT_RECONF_ACCEPT 20
+
+/*** Other shared functions ***/
+
+struct client6_data_t {
+	struct d6_option *server_id;
+	struct d6_option *ia_na;
+};
+
+#define client6_data (*(struct client6_data_t*)(&bb_common_bufsiz1[COMMON_BUFSIZE - sizeof(struct client6_data_t)]))
+
+int FAST_FUNC d6_listen_socket(int port, const char *inf);
+
+int FAST_FUNC d6_recv_kernel_packet(
+		struct in6_addr *peer_ipv6,
+		struct d6_packet *packet, int fd
+);
+
+int FAST_FUNC d6_send_raw_packet(
+		struct d6_packet *d6_pkt, unsigned d6_pkt_size,
+		struct in6_addr *src_ipv6, int source_port,
+		struct in6_addr *dst_ipv6, int dest_port, const uint8_t *dest_arp,
+		int ifindex
+);
+
+int FAST_FUNC d6_send_kernel_packet(
+		struct d6_packet *d6_pkt, unsigned d6_pkt_size,
+		struct in6_addr *src_ipv6, int source_port,
+		struct in6_addr *dst_ipv6, int dest_port
+);
+
+void FAST_FUNC d6_dump_packet(struct d6_packet *packet);
+
+
+POP_SAVED_FUNCTION_VISIBILITY
+
+#endif
diff --git a/networking/udhcp/d6_dhcpc.c b/networking/udhcp/d6_dhcpc.c
new file mode 100644
index 0000000..d1baaae
--- /dev/null
+++ b/networking/udhcp/d6_dhcpc.c
@@ -0,0 +1,1404 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * DHCPv6 client.
+ *
+ * 2011-11.
+ * WARNING: THIS CODE IS INCOMPLETE. IT IS NOWHERE NEAR
+ * TO BE READY FOR PRODUCTION USE.
+ *
+ * Copyright (C) 2011 Denys Vlasenko.
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+
+//config:config UDHCPC6
+//config:       bool "udhcp client for DHCPv6 (udhcpc6)"
+//config:       default n  # not yet ready
+//config:       help
+//config:         udhcpc6 is a DHCPv6 client
+
+//applet:IF_UDHCPC6(APPLET(udhcpc6, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_UDHCPC6) += d6_dhcpc.o d6_packet.o d6_socket.o common.o
+
+
+#include <syslog.h>
+/* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
+#define WANT_PIDFILE 1
+#include "common.h"
+#include "dhcpd.h"
+#include "dhcpc.h"
+#include "d6_common.h"
+
+#include <netinet/if_ether.h>
+#include <netpacket/packet.h>
+#include <linux/filter.h>
+
+/* "struct client_config_t client_config" is in bb_common_bufsiz1 */
+
+
+#if ENABLE_LONG_OPTS
+static const char udhcpc_longopts[] ALIGN1 =
+	"interface\0"      Required_argument "i"
+	"now\0"            No_argument       "n"
+	"pidfile\0"        Required_argument "p"
+	"quit\0"           No_argument       "q"
+	"release\0"        No_argument       "R"
+	"request\0"        Required_argument "r"
+	"script\0"         Required_argument "s"
+	"timeout\0"        Required_argument "T"
+	"version\0"        No_argument       "v"
+	"retries\0"        Required_argument "t"
+	"tryagain\0"       Required_argument "A"
+	"syslog\0"         No_argument       "S"
+	"request-option\0" Required_argument "O"
+	"no-default-options\0" No_argument   "o"
+	"foreground\0"     No_argument       "f"
+	"background\0"     No_argument       "b"
+	"broadcast\0"      No_argument       "B"
+///	IF_FEATURE_UDHCPC_ARPING("arping\0"	No_argument       "a")
+	IF_FEATURE_UDHCP_PORT("client-port\0"	Required_argument "P")
+	;
+#endif
+/* Must match getopt32 option string order */
+enum {
+	OPT_i = 1 << 0,
+	OPT_n = 1 << 1,
+	OPT_p = 1 << 2,
+	OPT_q = 1 << 3,
+	OPT_R = 1 << 4,
+	OPT_r = 1 << 5,
+	OPT_s = 1 << 6,
+	OPT_T = 1 << 7,
+	OPT_t = 1 << 8,
+	OPT_S = 1 << 9,
+	OPT_A = 1 << 10,
+	OPT_O = 1 << 11,
+	OPT_o = 1 << 12,
+	OPT_x = 1 << 13,
+	OPT_f = 1 << 14,
+	OPT_B = 1 << 15,
+/* The rest has variable bit positions, need to be clever */
+	OPTBIT_B = 15,
+	USE_FOR_MMU(             OPTBIT_b,)
+	///IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
+	IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
+	USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
+	///IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
+	IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
+};
+
+
+/*** Utility functions ***/
+
+static void *d6_find_option(uint8_t *option, uint8_t *option_end, unsigned code)
+{
+	/* "length minus 4" */
+	int len_m4 = option_end - option - 4;
+	while (len_m4 >= 0) {
+		/* Next option's len is too big? */
+		if (option[2] > len_m4)
+			return NULL; /* yes. bogus packet! */
+		/* So far we treat any opts with code >255
+		 * or len >255 as bogus, and stop at once.
+		 * This simplifies big-endian handling.
+		 */
+		if (option[1] != 0 || option[3] != 0)
+			return NULL;
+		/* Option seems to be valid */
+		/* Does its code match? */
+		if (option[0] == code)
+			return option; /* yes! */
+		option += option[2] + 4;
+		len_m4 -= option[2] + 4;
+	}
+	return NULL;
+}
+
+static void *d6_copy_option(uint8_t *option, uint8_t *option_end, unsigned code)
+{
+	uint8_t *opt = d6_find_option(option, option_end, code);
+	if (!opt)
+		return opt;
+	return memcpy(xmalloc(opt[2] + 4), opt, opt[2] + 4);
+}
+
+static void *d6_store_blob(void *dst, const void *src, unsigned len)
+{
+	memcpy(dst, src, len);
+	return dst + len;
+}
+
+
+/*** Script execution code ***/
+
+/* put all the parameters into the environment */
+static char **fill_envp(struct d6_packet *packet
+    UNUSED_PARAM
+)
+{
+	int envc;
+	char **envp, **curr;
+
+#define BITMAP unsigned
+#define BBITS (sizeof(BITMAP) * 8)
+#define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
+#define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
+	///BITMAP found_opts[256 / BBITS];
+
+	///memset(found_opts, 0, sizeof(found_opts));
+
+	/* We need 2 elements for:
+	 * "interface=IFACE"
+	 * terminating NULL
+	 */
+	envc = 2;
+
+	curr = envp = xzalloc(sizeof(envp[0]) * envc);
+
+	*curr = xasprintf("interface=%s", client_config.interface);
+	putenv(*curr++);
+
+	return envp;
+}
+
+/* Call a script with a par file and env vars */
+static void d6_run_script(struct d6_packet *packet, const char *name)
+{
+	char **envp, **curr;
+	char *argv[3];
+
+	envp = fill_envp(packet);
+
+	/* call script */
+	log1("Executing %s %s", client_config.script, name);
+	argv[0] = (char*) client_config.script;
+	argv[1] = (char*) name;
+	argv[2] = NULL;
+	spawn_and_wait(argv);
+
+	for (curr = envp; *curr; curr++) {
+		log2(" %s", *curr);
+		bb_unsetenv_and_free(*curr);
+	}
+	free(envp);
+}
+
+
+/*** Sending/receiving packets ***/
+
+static ALWAYS_INLINE uint32_t random_xid(void)
+{
+	uint32_t t = rand() & htonl(0x00ffffff);
+	return t;
+}
+
+/* Initialize the packet with the proper defaults */
+static uint8_t *init_d6_packet(struct d6_packet *packet, char type, uint32_t xid)
+{
+	struct d6_option *clientid;
+
+	memset(packet, 0, sizeof(*packet));
+
+	packet->d6_xid32 = xid;
+	packet->d6_msg_type = type;
+
+	clientid = (void*)client_config.clientid;
+	return d6_store_blob(packet->d6_options, clientid, clientid->len + 2+2);
+}
+
+static uint8_t *add_d6_client_options(uint8_t *ptr)
+{
+	return ptr;
+	//uint8_t c;
+	//int i, end, len;
+
+	/* Add a "param req" option with the list of options we'd like to have
+	 * from stubborn DHCP servers. Pull the data from the struct in common.c.
+	 * No bounds checking because it goes towards the head of the packet. */
+	//...
+
+	/* Add -x options if any */
+	//...
+}
+
+static int d6_mcast_from_client_config_ifindex(struct d6_packet *packet, uint8_t *end)
+{
+	static const uint8_t FF02__1_2[16] = {
+		0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x02,
+	};
+
+	return d6_send_raw_packet(
+		packet, (end - (uint8_t*) packet),
+		/*src*/ NULL, CLIENT_PORT,
+		/*dst*/ (struct in6_addr*)FF02__1_2, SERVER_PORT, MAC_BCAST_ADDR,
+		client_config.ifindex
+	);
+}
+
+/* Milticast a DHCPv6 Solicit packet to the network, with an optionally requested IP.
+ *
+ * RFC 3315 17.1.1. Creation of Solicit Messages
+ *
+ * The client MUST include a Client Identifier option to identify itself
+ * to the server.  The client includes IA options for any IAs to which
+ * it wants the server to assign addresses.  The client MAY include
+ * addresses in the IAs as a hint to the server about addresses for
+ * which the client has a preference. ...
+ *
+ * The client uses IA_NA options to request the assignment of non-
+ * temporary addresses and uses IA_TA options to request the assignment
+ * of temporary addresses.  Either IA_NA or IA_TA options, or a
+ * combination of both, can be included in DHCP messages.
+ *
+ * The client SHOULD include an Option Request option (see section 22.7)
+ * to indicate the options the client is interested in receiving.  The
+ * client MAY additionally include instances of those options that are
+ * identified in the Option Request option, with data values as hints to
+ * the server about parameter values the client would like to have
+ * returned.
+ *
+ * The client includes a Reconfigure Accept option (see section 22.20)
+ * if the client is willing to accept Reconfigure messages from the
+ * server.
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |        OPTION_CLIENTID        |          option-len           |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      .                                                               .
+      .                              DUID                             .
+      .                        (variable length)                      .
+      .                                                               .
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |          OPTION_IA_NA         |          option-len           |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |                        IAID (4 octets)                        |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |                              T1                               |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |                              T2                               |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |                                                               |
+      .                         IA_NA-options                         .
+      .                                                               .
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |          OPTION_IAADDR        |          option-len           |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |                                                               |
+      |                         IPv6 address                          |
+      |                                                               |
+      |                                                               |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |                      preferred-lifetime                       |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |                        valid-lifetime                         |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      .                                                               .
+      .                        IAaddr-options                         .
+      .                                                               .
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |           OPTION_ORO          |           option-len          |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |    requested-option-code-1    |    requested-option-code-2    |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |                              ...                              |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |     OPTION_RECONF_ACCEPT      |               0               |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+/* NOINLINE: limit stack usage in caller */
+static NOINLINE int send_d6_discover(uint32_t xid, struct in6_addr *requested_ipv6)
+{
+	struct d6_packet packet;
+	uint8_t *opt_ptr;
+	unsigned len;
+
+	/* Fill in: msg type, client id */
+	opt_ptr = init_d6_packet(&packet, D6_MSG_SOLICIT, xid);
+
+	/* Create new IA_NA, optionally with included IAADDR with requested IP */
+	free(client6_data.ia_na);
+	len = requested_ipv6 ? 2+2+4+4+4 + 2+2+16+4+4 : 2+2+4+4+4;
+	client6_data.ia_na = xzalloc(len);
+	client6_data.ia_na->code = D6_OPT_IA_NA;
+	client6_data.ia_na->len = len - 4;
+	*(uint32_t*)client6_data.ia_na->data = rand(); /* IAID */
+	if (requested_ipv6) {
+		struct d6_option *iaaddr = (void*)(client6_data.ia_na->data + 4+4+4);
+		iaaddr->code = D6_OPT_IAADDR;
+		iaaddr->len = 16+4+4;
+		memcpy(iaaddr->data, requested_ipv6, 16);
+	}
+	opt_ptr = d6_store_blob(opt_ptr, client6_data.ia_na, len);
+
+	/* Add options:
+	 * "param req" option according to -O, options specified with -x
+	 */
+	opt_ptr = add_d6_client_options(opt_ptr);
+
+	bb_info_msg("Sending discover...");
+	return d6_mcast_from_client_config_ifindex(&packet, opt_ptr);
+}
+
+/* Multicast a DHCPv6 request message
+ *
+ * RFC 3315 18.1.1. Creation and Transmission of Request Messages
+ *
+ * The client uses a Request message to populate IAs with addresses and
+ * obtain other configuration information.  The client includes one or
+ * more IA options in the Request message.  The server then returns
+ * addresses and other information about the IAs to the client in IA
+ * options in a Reply message.
+ *
+ * The client generates a transaction ID and inserts this value in the
+ * "transaction-id" field.
+ *
+ * The client places the identifier of the destination server in a
+ * Server Identifier option.
+ *
+ * The client MUST include a Client Identifier option to identify itself
+ * to the server.  The client adds any other appropriate options,
+ * including one or more IA options (if the client is requesting that
+ * the server assign it some network addresses).
+ *
+ * The client MUST include an Option Request option (see section 22.7)
+ * to indicate the options the client is interested in receiving.  The
+ * client MAY include options with data values as hints to the server
+ * about parameter values the client would like to have returned.
+ *
+ * The client includes a Reconfigure Accept option (see section 22.20)
+ * indicating whether or not the client is willing to accept Reconfigure
+ * messages from the server.
+ */
+/* NOINLINE: limit stack usage in caller */
+static NOINLINE int send_d6_select(uint32_t xid)
+{
+	struct d6_packet packet;
+	uint8_t *opt_ptr;
+
+	/* Fill in: msg type, client id */
+	opt_ptr = init_d6_packet(&packet, D6_MSG_REQUEST, xid);
+
+	/* server id */
+	opt_ptr = d6_store_blob(opt_ptr, client6_data.server_id, client6_data.server_id->len + 2+2);
+	/* IA NA (contains requested IP) */
+	opt_ptr = d6_store_blob(opt_ptr, client6_data.ia_na, client6_data.ia_na->len + 2+2);
+
+	/* Add options:
+	 * "param req" option according to -O, options specified with -x
+	 */
+	opt_ptr = add_d6_client_options(opt_ptr);
+
+	bb_info_msg("Sending select...");
+	return d6_mcast_from_client_config_ifindex(&packet, opt_ptr);
+}
+
+/* Unicast or broadcast a DHCP renew message
+ *
+ * RFC 3315 18.1.3. Creation and Transmission of Renew Messages
+ *
+ * To extend the valid and preferred lifetimes for the addresses
+ * associated with an IA, the client sends a Renew message to the server
+ * from which the client obtained the addresses in the IA containing an
+ * IA option for the IA.  The client includes IA Address options in the
+ * IA option for the addresses associated with the IA.  The server
+ * determines new lifetimes for the addresses in the IA according to the
+ * administrative configuration of the server.  The server may also add
+ * new addresses to the IA.  The server may remove addresses from the IA
+ * by setting the preferred and valid lifetimes of those addresses to
+ * zero.
+ *
+ * The server controls the time at which the client contacts the server
+ * to extend the lifetimes on assigned addresses through the T1 and T2
+ * parameters assigned to an IA.
+ *
+ * At time T1 for an IA, the client initiates a Renew/Reply message
+ * exchange to extend the lifetimes on any addresses in the IA.  The
+ * client includes an IA option with all addresses currently assigned to
+ * the IA in its Renew message.
+ *
+ * If T1 or T2 is set to 0 by the server (for an IA_NA) or there are no
+ * T1 or T2 times (for an IA_TA), the client may send a Renew or Rebind
+ * message, respectively, at the client's discretion.
+ *
+ * The client sets the "msg-type" field to RENEW.  The client generates
+ * a transaction ID and inserts this value in the "transaction-id"
+ * field.
+ *
+ * The client places the identifier of the destination server in a
+ * Server Identifier option.
+ *
+ * The client MUST include a Client Identifier option to identify itself
+ * to the server.  The client adds any appropriate options, including
+ * one or more IA options.  The client MUST include the list of
+ * addresses the client currently has associated with the IAs in the
+ * Renew message.
+ *
+ * The client MUST include an Option Request option (see section 22.7)
+ * to indicate the options the client is interested in receiving.  The
+ * client MAY include options with data values as hints to the server
+ * about parameter values the client would like to have returned.
+ */
+/* NOINLINE: limit stack usage in caller */
+static NOINLINE int send_d6_renew(uint32_t xid, struct in6_addr *server_ipv6, struct in6_addr *our_cur_ipv6)
+{
+	struct d6_packet packet;
+	uint8_t *opt_ptr;
+
+	/* Fill in: msg type, client id */
+	opt_ptr = init_d6_packet(&packet, DHCPREQUEST, xid);
+
+	/* server id */
+	opt_ptr = d6_store_blob(opt_ptr, client6_data.server_id, client6_data.server_id->len + 2+2);
+	/* IA NA (contains requested IP) */
+	opt_ptr = d6_store_blob(opt_ptr, client6_data.ia_na, client6_data.ia_na->len + 2+2);
+
+	/* Add options:
+	 * "param req" option according to -O, options specified with -x
+	 */
+	opt_ptr = add_d6_client_options(opt_ptr);
+
+	bb_info_msg("Sending renew...");
+	if (server_ipv6)
+		return d6_send_kernel_packet(
+			&packet, (opt_ptr - (uint8_t*) &packet),
+			our_cur_ipv6, CLIENT_PORT,
+			server_ipv6, SERVER_PORT
+		);
+	return d6_mcast_from_client_config_ifindex(&packet, opt_ptr);
+}
+
+/* Unicast a DHCP release message */
+static int send_d6_release(struct in6_addr *server_ipv6, struct in6_addr *our_cur_ipv6)
+{
+	struct d6_packet packet;
+	uint8_t *opt_ptr;
+
+	/* Fill in: msg type, client id */
+	opt_ptr = init_d6_packet(&packet, D6_MSG_RELEASE, random_xid());
+	/* server id */
+	opt_ptr = d6_store_blob(opt_ptr, client6_data.server_id, client6_data.server_id->len + 2+2);
+	/* IA NA (contains our current IP) */
+	opt_ptr = d6_store_blob(opt_ptr, client6_data.ia_na, client6_data.ia_na->len + 2+2);
+
+	bb_info_msg("Sending release...");
+	return d6_send_kernel_packet(
+		&packet, (opt_ptr - (uint8_t*) &packet),
+		our_cur_ipv6, CLIENT_PORT,
+		server_ipv6, SERVER_PORT
+	);
+}
+
+/* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
+/* NOINLINE: limit stack usage in caller */
+static NOINLINE int d6_recv_raw_packet(struct in6_addr *peer_ipv6
+	UNUSED_PARAM
+	, struct d6_packet *d6_pkt, int fd)
+{
+	int bytes;
+	struct ip6_udp_d6_packet packet;
+
+	bytes = safe_read(fd, &packet, sizeof(packet));
+	if (bytes < 0) {
+		log1("Packet read error, ignoring");
+		/* NB: possible down interface, etc. Caller should pause. */
+		return bytes; /* returns -1 */
+	}
+
+	if (bytes < (int) (sizeof(packet.ip6) + sizeof(packet.udp))) {
+		log1("Packet is too short, ignoring");
+		return -2;
+	}
+
+	if (bytes < sizeof(packet.ip6) + ntohs(packet.ip6.ip6_plen)) {
+		/* packet is bigger than sizeof(packet), we did partial read */
+		log1("Oversized packet, ignoring");
+		return -2;
+	}
+
+	/* ignore any extra garbage bytes */
+	bytes = sizeof(packet.ip6) + ntohs(packet.ip6.ip6_plen);
+
+	/* make sure its the right packet for us, and that it passes sanity checks */
+	if (packet.ip6.ip6_nxt != IPPROTO_UDP
+	 || (packet.ip6.ip6_vfc >> 4) != 6
+	 || packet.udp.dest != htons(CLIENT_PORT)
+	/* || bytes > (int) sizeof(packet) - can't happen */
+	 || packet.udp.len != packet.ip6.ip6_plen
+	) {
+		log1("Unrelated/bogus packet, ignoring");
+		return -2;
+	}
+
+//How to do this for ipv6?
+//	/* verify UDP checksum. IP header has to be modified for this */
+//	memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
+//	/* ip.xx fields which are not memset: protocol, check, saddr, daddr */
+//	packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
+//	check = packet.udp.check;
+//	packet.udp.check = 0;
+//	if (check && check != inet_cksum((uint16_t *)&packet, bytes)) {
+//		log1("Packet with bad UDP checksum received, ignoring");
+//		return -2;
+//	}
+
+	log1("Received a packet");
+	d6_dump_packet(&packet.data);
+
+	bytes -= sizeof(packet.ip6) + sizeof(packet.udp);
+	memcpy(d6_pkt, &packet.data, bytes);
+	return bytes;
+}
+
+
+/*** Main ***/
+
+static int sockfd = -1;
+
+#define LISTEN_NONE   0
+#define LISTEN_KERNEL 1
+#define LISTEN_RAW    2
+static smallint listen_mode;
+
+/* initial state: (re)start DHCP negotiation */
+#define INIT_SELECTING  0
+/* discover was sent, DHCPOFFER reply received */
+#define REQUESTING      1
+/* select/renew was sent, DHCPACK reply received */
+#define BOUND           2
+/* half of lease passed, want to renew it by sending unicast renew requests */
+#define RENEWING        3
+/* renew requests were not answered, lease is almost over, send broadcast renew */
+#define REBINDING       4
+/* manually requested renew (SIGUSR1) */
+#define RENEW_REQUESTED 5
+/* release, possibly manually requested (SIGUSR2) */
+#define RELEASED        6
+static smallint state;
+
+static int d6_raw_socket(int ifindex)
+{
+	int fd;
+	struct sockaddr_ll sock;
+
+	/*
+	 * Comment:
+	 *
+	 *	I've selected not to see LL header, so BPF doesn't see it, too.
+	 *	The filter may also pass non-IP and non-ARP packets, but we do
+	 *	a more complete check when receiving the message in userspace.
+	 *
+	 * and filter shamelessly stolen from:
+	 *
+	 *	http://www.flamewarmaster.de/software/dhcpclient/
+	 *
+	 * There are a few other interesting ideas on that page (look under
+	 * "Motivation").  Use of netlink events is most interesting.  Think
+	 * of various network servers listening for events and reconfiguring.
+	 * That would obsolete sending HUP signals and/or make use of restarts.
+	 *
+	 * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
+	 * License: GPL v2.
+	 *
+	 * TODO: make conditional?
+	 */
+#if 0
+	static const struct sock_filter filter_instr[] = {
+		/* load 9th byte (protocol) */
+		BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
+		/* jump to L1 if it is IPPROTO_UDP, else to L4 */
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
+		/* L1: load halfword from offset 6 (flags and frag offset) */
+		BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
+		/* jump to L4 if any bits in frag offset field are set, else to L2 */
+		BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
+		/* L2: skip IP header (load index reg with header len) */
+		BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
+		/* load udp destination port from halfword[header_len + 2] */
+		BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
+		/* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
+		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
+		/* L3: accept packet */
+		BPF_STMT(BPF_RET|BPF_K, 0xffffffff),
+		/* L4: discard packet */
+		BPF_STMT(BPF_RET|BPF_K, 0),
+	};
+	static const struct sock_fprog filter_prog = {
+		.len = sizeof(filter_instr) / sizeof(filter_instr[0]),
+		/* casting const away: */
+		.filter = (struct sock_filter *) filter_instr,
+	};
+#endif
+
+	log1("Opening raw socket on ifindex %d", ifindex); //log2?
+
+	fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IPV6));
+	log1("Got raw socket fd %d", fd); //log2?
+
+	sock.sll_family = AF_PACKET;
+	sock.sll_protocol = htons(ETH_P_IPV6);
+	sock.sll_ifindex = ifindex;
+	xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
+
+#if 0
+	if (CLIENT_PORT == 68) {
+		/* Use only if standard port is in use */
+		/* Ignoring error (kernel may lack support for this) */
+		if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
+				sizeof(filter_prog)) >= 0)
+			log1("Attached filter to raw socket fd %d", fd); // log?
+	}
+#endif
+
+	log1("Created raw socket");
+
+	return fd;
+}
+
+static void change_listen_mode(int new_mode)
+{
+	log1("Entering listen mode: %s",
+		new_mode != LISTEN_NONE
+			? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
+			: "none"
+	);
+
+	listen_mode = new_mode;
+	if (sockfd >= 0) {
+		close(sockfd);
+		sockfd = -1;
+	}
+	if (new_mode == LISTEN_KERNEL)
+		sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
+	else if (new_mode != LISTEN_NONE)
+		sockfd = d6_raw_socket(client_config.ifindex);
+	/* else LISTEN_NONE: sockfd stays closed */
+}
+
+/* Called only on SIGUSR1 */
+static void perform_renew(void)
+{
+	bb_info_msg("Performing a DHCP renew");
+	switch (state) {
+	case BOUND:
+		change_listen_mode(LISTEN_KERNEL);
+	case RENEWING:
+	case REBINDING:
+		state = RENEW_REQUESTED;
+		break;
+	case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
+		d6_run_script(NULL, "deconfig");
+	case REQUESTING:
+	case RELEASED:
+		change_listen_mode(LISTEN_RAW);
+		state = INIT_SELECTING;
+		break;
+	case INIT_SELECTING:
+		break;
+	}
+}
+
+static void perform_d6_release(struct in6_addr *server_ipv6, struct in6_addr *our_cur_ipv6)
+{
+	/* send release packet */
+	if (state == BOUND || state == RENEWING || state == REBINDING) {
+		bb_info_msg("Unicasting a release");
+		send_d6_release(server_ipv6, our_cur_ipv6); /* unicast */
+		d6_run_script(NULL, "deconfig");
+	}
+	bb_info_msg("Entering released state");
+
+	change_listen_mode(LISTEN_NONE);
+	state = RELEASED;
+}
+
+///static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
+///{
+///	uint8_t *storage;
+///	int len = strnlen(str, 255);
+///	storage = xzalloc(len + extra + OPT_DATA);
+///	storage[OPT_CODE] = code;
+///	storage[OPT_LEN] = len + extra;
+///	memcpy(storage + extra + OPT_DATA, str, len);
+///	return storage;
+///}
+
+#if BB_MMU
+static void client_background(void)
+{
+	bb_daemonize(0);
+	logmode &= ~LOGMODE_STDIO;
+	/* rewrite pidfile, as our pid is different now */
+	write_pidfile(client_config.pidfile);
+}
+#endif
+
+//usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
+//usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__
+//usage:#else
+//usage:# define IF_UDHCP_VERBOSE(...)
+//usage:#endif
+//usage:#define udhcpc6_trivial_usage
+//usage:       "[-fbnq"IF_UDHCP_VERBOSE("v")"oRB] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]\n"
+//usage:       "	[-x OPT:VAL]... [-O OPT]..." IF_FEATURE_UDHCP_PORT(" [-P N]")
+//usage:#define udhcpc6_full_usage "\n"
+//usage:	IF_LONG_OPTS(
+//usage:     "\n	-i,--interface IFACE	Interface to use (default eth0)"
+//usage:     "\n	-p,--pidfile FILE	Create pidfile"
+//usage:     "\n	-s,--script PROG	Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
+//usage:     "\n	-B,--broadcast		Request broadcast replies"
+//usage:     "\n	-t,--retries N		Send up to N discover packets"
+//usage:     "\n	-T,--timeout N		Pause between packets (default 3 seconds)"
+//usage:     "\n	-A,--tryagain N		Wait N seconds after failure (default 20)"
+//usage:     "\n	-f,--foreground		Run in foreground"
+//usage:	USE_FOR_MMU(
+//usage:     "\n	-b,--background		Background if lease is not obtained"
+//usage:	)
+//usage:     "\n	-n,--now		Exit if lease is not obtained"
+//usage:     "\n	-q,--quit		Exit after obtaining lease"
+//usage:     "\n	-R,--release		Release IP on exit"
+//usage:     "\n	-S,--syslog		Log to syslog too"
+//usage:	IF_FEATURE_UDHCP_PORT(
+//usage:     "\n	-P,--client-port N	Use port N (default 68)"
+//usage:	)
+////usage:	IF_FEATURE_UDHCPC_ARPING(
+////usage:     "\n	-a,--arping		Use arping to validate offered address"
+////usage:	)
+//usage:     "\n	-O,--request-option OPT	Request option OPT from server (cumulative)"
+//usage:     "\n	-o,--no-default-options	Don't request any options (unless -O is given)"
+//usage:     "\n	-r,--request IP		Request this IP address"
+//usage:     "\n	-x OPT:VAL		Include option OPT in sent packets (cumulative)"
+//usage:     "\n				Examples of string, numeric, and hex byte opts:"
+//usage:     "\n				-x hostname:bbox - option 12"
+//usage:     "\n				-x lease:3600 - option 51 (lease time)"
+//usage:     "\n				-x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
+//usage:	IF_UDHCP_VERBOSE(
+//usage:     "\n	-v			Verbose"
+//usage:	)
+//usage:	)
+//usage:	IF_NOT_LONG_OPTS(
+//usage:     "\n	-i IFACE	Interface to use (default eth0)"
+//usage:     "\n	-p FILE		Create pidfile"
+//usage:     "\n	-s PROG		Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
+//usage:     "\n	-B		Request broadcast replies"
+//usage:     "\n	-t N		Send up to N discover packets"
+//usage:     "\n	-T N		Pause between packets (default 3 seconds)"
+//usage:     "\n	-A N		Wait N seconds (default 20) after failure"
+//usage:     "\n	-f		Run in foreground"
+//usage:	USE_FOR_MMU(
+//usage:     "\n	-b		Background if lease is not obtained"
+//usage:	)
+//usage:     "\n	-n		Exit if lease is not obtained"
+//usage:     "\n	-q		Exit after obtaining lease"
+//usage:     "\n	-R		Release IP on exit"
+//usage:     "\n	-S		Log to syslog too"
+//usage:	IF_FEATURE_UDHCP_PORT(
+//usage:     "\n	-P N		Use port N (default 68)"
+//usage:	)
+////usage:	IF_FEATURE_UDHCPC_ARPING(
+////usage:     "\n	-a		Use arping to validate offered address"
+////usage:	)
+//usage:     "\n	-O OPT		Request option OPT from server (cumulative)"
+//usage:     "\n	-o		Don't request any options (unless -O is given)"
+//usage:     "\n	-r IP		Request this IP address"
+//usage:     "\n	-x OPT:VAL	Include option OPT in sent packets (cumulative)"
+//usage:     "\n			Examples of string, numeric, and hex byte opts:"
+//usage:     "\n			-x hostname:bbox - option 12"
+//usage:     "\n			-x lease:3600 - option 51 (lease time)"
+//usage:     "\n			-x 0x3d:0100BEEFC0FFEE - option 61 (client id)"
+//usage:	IF_UDHCP_VERBOSE(
+//usage:     "\n	-v		Verbose"
+//usage:	)
+//usage:	)
+//usage:     "\nSignals:"
+//usage:     "\n	USR1	Renew lease"
+//usage:     "\n	USR2	Release lease"
+
+
+int udhcpc6_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
+{
+	const char *str_r;
+	IF_FEATURE_UDHCP_PORT(char *str_P;)
+	void *clientid_mac_ptr;
+	llist_t *list_O = NULL;
+	llist_t *list_x = NULL;
+	int tryagain_timeout = 20;
+	int discover_timeout = 3;
+	int discover_retries = 3;
+	struct in6_addr srv6_buf;
+	struct in6_addr ipv6_buf;
+	struct in6_addr *requested_ipv6;
+	uint32_t xid = 0;
+	int packet_num;
+	int timeout; /* must be signed */
+	unsigned already_waited_sec;
+	unsigned opt;
+	int max_fd;
+	int retval;
+	fd_set rfds;
+
+	/* Default options */
+	IF_FEATURE_UDHCP_PORT(SERVER_PORT = 547;)
+	IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 546;)
+	client_config.interface = "eth0";
+	client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT;
+
+	/* Parse command line */
+	/* O,x: list; -T,-t,-A take numeric param */
+	opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ;
+	IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
+	opt = getopt32(argv, "i:np:qRr:s:T:t:SA:O:ox:fB"
+		USE_FOR_MMU("b")
+		///IF_FEATURE_UDHCPC_ARPING("a")
+		IF_FEATURE_UDHCP_PORT("P:")
+		"v"
+		, &client_config.interface, &client_config.pidfile, &str_r /* i,p */
+		, &client_config.script /* s */
+		, &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
+		, &list_O
+		, &list_x
+		IF_FEATURE_UDHCP_PORT(, &str_P)
+		IF_UDHCP_VERBOSE(, &dhcp_verbose)
+		);
+	requested_ipv6 = NULL;
+	if (opt & OPT_r) {
+		if (inet_pton(AF_INET6, str_r, &ipv6_buf) <= 0)
+			bb_error_msg_and_die("bad IPv6 address '%s'", str_r);
+		requested_ipv6 = &ipv6_buf;
+	}
+#if ENABLE_FEATURE_UDHCP_PORT
+	if (opt & OPT_P) {
+		CLIENT_PORT = xatou16(str_P);
+		SERVER_PORT = CLIENT_PORT - 1;
+	}
+#endif
+	if (opt & OPT_o)
+		client_config.no_default_options = 1;
+	while (list_O) {
+		char *optstr = llist_pop(&list_O);
+		unsigned n = bb_strtou(optstr, NULL, 0);
+		if (errno || n > 254) {
+			n = udhcp_option_idx(optstr);
+			n = dhcp_optflags[n].code;
+		}
+		client_config.opt_mask[n >> 3] |= 1 << (n & 7);
+	}
+	while (list_x) {
+		char *optstr = llist_pop(&list_x);
+		char *colon = strchr(optstr, ':');
+		if (colon)
+			*colon = ' ';
+		/* now it looks similar to udhcpd's config file line:
+		 * "optname optval", using the common routine: */
+		udhcp_str2optset(optstr, &client_config.options);
+	}
+
+	if (udhcp_read_interface(client_config.interface,
+			&client_config.ifindex,
+			NULL,
+			client_config.client_mac)
+	) {
+		return 1;
+	}
+
+	/* Create client ID based on mac, set clientid_mac_ptr */
+	{
+		struct d6_option *clientid;
+		clientid = xzalloc(2+2+2+2+6);
+		clientid->code = D6_OPT_CLIENTID;
+		clientid->len = 2+2+6;
+		clientid->data[0] = 3; /* DUID-LL */
+		clientid->data[2] = 1; /* ethernet */
+		clientid_mac_ptr = clientid->data + 2+2;
+		memcpy(clientid_mac_ptr, client_config.client_mac, 6);
+		client_config.clientid = (void*)clientid;
+	}
+
+#if !BB_MMU
+	/* on NOMMU reexec (i.e., background) early */
+	if (!(opt & OPT_f)) {
+		bb_daemonize_or_rexec(0 /* flags */, argv);
+		logmode = LOGMODE_NONE;
+	}
+#endif
+	if (opt & OPT_S) {
+		openlog(applet_name, LOG_PID, LOG_DAEMON);
+		logmode |= LOGMODE_SYSLOG;
+	}
+
+	/* Make sure fd 0,1,2 are open */
+	bb_sanitize_stdio();
+	/* Equivalent of doing a fflush after every \n */
+	setlinebuf(stdout);
+	/* Create pidfile */
+	write_pidfile(client_config.pidfile);
+	/* Goes to stdout (unless NOMMU) and possibly syslog */
+	bb_info_msg("%s (v"BB_VER") started", applet_name);
+	/* Set up the signal pipe */
+	udhcp_sp_setup();
+	/* We want random_xid to be random... */
+	srand(monotonic_us());
+
+	state = INIT_SELECTING;
+	d6_run_script(NULL, "deconfig");
+	change_listen_mode(LISTEN_RAW);
+	packet_num = 0;
+	timeout = 0;
+	already_waited_sec = 0;
+
+	/* Main event loop. select() waits on signal pipe and possibly
+	 * on sockfd.
+	 * "continue" statements in code below jump to the top of the loop.
+	 */
+	for (;;) {
+		struct timeval tv;
+		struct d6_packet packet;
+		uint8_t *packet_end;
+		/* silence "uninitialized!" warning */
+		unsigned timestamp_before_wait = timestamp_before_wait;
+
+		//bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
+
+		/* Was opening raw or udp socket here
+		 * if (listen_mode != LISTEN_NONE && sockfd < 0),
+		 * but on fast network renew responses return faster
+		 * than we open sockets. Thus this code is moved
+		 * to change_listen_mode(). Thus we open listen socket
+		 * BEFORE we send renew request (see "case BOUND:"). */
+
+		max_fd = udhcp_sp_fd_set(&rfds, sockfd);
+
+		tv.tv_sec = timeout - already_waited_sec;
+		tv.tv_usec = 0;
+		retval = 0;
+		/* If we already timed out, fall through with retval = 0, else... */
+		if ((int)tv.tv_sec > 0) {
+			timestamp_before_wait = (unsigned)monotonic_sec();
+			log1("Waiting on select...");
+			retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
+			if (retval < 0) {
+				/* EINTR? A signal was caught, don't panic */
+				if (errno == EINTR) {
+					already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
+					continue;
+				}
+				/* Else: an error occured, panic! */
+				bb_perror_msg_and_die("select");
+			}
+		}
+
+		/* If timeout dropped to zero, time to become active:
+		 * resend discover/renew/whatever
+		 */
+		if (retval == 0) {
+			/* When running on a bridge, the ifindex may have changed
+			 * (e.g. if member interfaces were added/removed
+			 * or if the status of the bridge changed).
+			 * Refresh ifindex and client_mac:
+			 */
+			if (udhcp_read_interface(client_config.interface,
+					&client_config.ifindex,
+					NULL,
+					client_config.client_mac)
+			) {
+				goto ret0; /* iface is gone? */
+			}
+			memcpy(clientid_mac_ptr, client_config.client_mac, 6);
+
+			/* We will restart the wait in any case */
+			already_waited_sec = 0;
+
+			switch (state) {
+			case INIT_SELECTING:
+				if (packet_num < discover_retries) {
+					if (packet_num == 0)
+						xid = random_xid();
+					/* multicast */
+					send_d6_discover(xid, requested_ipv6);
+					timeout = discover_timeout;
+					packet_num++;
+					continue;
+				}
+ leasefail:
+				d6_run_script(NULL, "leasefail");
+#if BB_MMU /* -b is not supported on NOMMU */
+				if (opt & OPT_b) { /* background if no lease */
+					bb_info_msg("No lease, forking to background");
+					client_background();
+					/* do not background again! */
+					opt = ((opt & ~OPT_b) | OPT_f);
+				} else
+#endif
+				if (opt & OPT_n) { /* abort if no lease */
+					bb_info_msg("No lease, failing");
+					retval = 1;
+					goto ret;
+				}
+				/* wait before trying again */
+				timeout = tryagain_timeout;
+				packet_num = 0;
+				continue;
+			case REQUESTING:
+				if (packet_num < discover_retries) {
+					/* send multicast select packet */
+					send_d6_select(xid);
+					timeout = discover_timeout;
+					packet_num++;
+					continue;
+				}
+				/* Timed out, go back to init state.
+				 * "discover...select...discover..." loops
+				 * were seen in the wild. Treat them similarly
+				 * to "no response to discover" case */
+				change_listen_mode(LISTEN_RAW);
+				state = INIT_SELECTING;
+				goto leasefail;
+			case BOUND:
+				/* 1/2 lease passed, enter renewing state */
+				state = RENEWING;
+				client_config.first_secs = 0; /* make secs field count from 0 */
+				change_listen_mode(LISTEN_KERNEL);
+				log1("Entering renew state");
+				/* fall right through */
+			case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
+			case_RENEW_REQUESTED:
+			case RENEWING:
+				if (timeout > 60) {
+					/* send an unicast renew request */
+			/* Sometimes observed to fail (EADDRNOTAVAIL) to bind
+			 * a new UDP socket for sending inside send_renew.
+			 * I hazard to guess existing listening socket
+			 * is somehow conflicting with it, but why is it
+			 * not deterministic then?! Strange.
+			 * Anyway, it does recover by eventually failing through
+			 * into INIT_SELECTING state.
+			 */
+					send_d6_renew(xid, &srv6_buf, requested_ipv6);
+					timeout >>= 1;
+					continue;
+				}
+				/* Timed out, enter rebinding state */
+				log1("Entering rebinding state");
+				state = REBINDING;
+				/* fall right through */
+			case REBINDING:
+				/* Switch to bcast receive */
+				change_listen_mode(LISTEN_RAW);
+				/* Lease is *really* about to run out,
+				 * try to find DHCP server using broadcast */
+				if (timeout > 0) {
+					/* send a broadcast renew request */
+					send_d6_renew(xid, /*server_ipv6:*/ NULL, requested_ipv6);
+					timeout >>= 1;
+					continue;
+				}
+				/* Timed out, enter init state */
+				bb_info_msg("Lease lost, entering init state");
+				d6_run_script(NULL, "deconfig");
+				state = INIT_SELECTING;
+				client_config.first_secs = 0; /* make secs field count from 0 */
+				/*timeout = 0; - already is */
+				packet_num = 0;
+				continue;
+			/* case RELEASED: */
+			}
+			/* yah, I know, *you* say it would never happen */
+			timeout = INT_MAX;
+			continue; /* back to main loop */
+		} /* if select timed out */
+
+		/* select() didn't timeout, something happened */
+
+		/* Is it a signal? */
+		/* note: udhcp_sp_read checks FD_ISSET before reading */
+		switch (udhcp_sp_read(&rfds)) {
+		case SIGUSR1:
+			client_config.first_secs = 0; /* make secs field count from 0 */
+			already_waited_sec = 0;
+			perform_renew();
+			if (state == RENEW_REQUESTED) {
+				/* We might be either on the same network
+				 * (in which case renew might work),
+				 * or we might be on a completely different one
+				 * (in which case renew won't ever succeed).
+				 * For the second case, must make sure timeout
+				 * is not too big, or else we can send
+				 * futile renew requests for hours.
+				 * (Ab)use -A TIMEOUT value (usually 20 sec)
+				 * as a cap on the timeout.
+				 */
+				if (timeout > tryagain_timeout)
+					timeout = tryagain_timeout;
+				goto case_RENEW_REQUESTED;
+			}
+			/* Start things over */
+			packet_num = 0;
+			/* Kill any timeouts, user wants this to hurry along */
+			timeout = 0;
+			continue;
+		case SIGUSR2:
+			perform_d6_release(&srv6_buf, requested_ipv6);
+			timeout = INT_MAX;
+			continue;
+		case SIGTERM:
+			bb_info_msg("Received SIGTERM");
+			goto ret0;
+		}
+
+		/* Is it a packet? */
+		if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
+			continue; /* no */
+
+		{
+			int len;
+
+			/* A packet is ready, read it */
+			if (listen_mode == LISTEN_KERNEL)
+				len = d6_recv_kernel_packet(&srv6_buf, &packet, sockfd);
+			else
+				len = d6_recv_raw_packet(&srv6_buf, &packet, sockfd);
+			if (len == -1) {
+				/* Error is severe, reopen socket */
+				bb_info_msg("Read error: %s, reopening socket", strerror(errno));
+				sleep(discover_timeout); /* 3 seconds by default */
+				change_listen_mode(listen_mode); /* just close and reopen */
+			}
+			/* If this packet will turn out to be unrelated/bogus,
+			 * we will go back and wait for next one.
+			 * Be sure timeout is properly decreased. */
+			already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
+			if (len < 0)
+				continue;
+			packet_end = (uint8_t*)&packet + len;
+		}
+
+		if ((packet.d6_xid32 & htonl(0x00ffffff)) != xid) {
+			log1("xid %x (our is %x), ignoring packet",
+				(unsigned)(packet.d6_xid32 & htonl(0x00ffffff)), (unsigned)xid);
+			continue;
+		}
+
+		switch (state) {
+		case INIT_SELECTING:
+			if (packet.d6_msg_type == D6_MSG_ADVERTISE)
+				goto type_is_ok;
+			/* DHCPv6 has "Rapid Commit", when instead of Advertise,
+			 * server sends Reply right away.
+			 * Fall through to check for this case.
+			 */
+		case REQUESTING:
+		case RENEWING:
+		case RENEW_REQUESTED:
+		case REBINDING:
+			if (packet.d6_msg_type == D6_MSG_REPLY) {
+				uint32_t lease_seconds;
+				struct d6_option *option, *iaaddr;
+ type_is_ok:
+				option = d6_find_option(packet.d6_options, packet_end, D6_OPT_STATUS_CODE);
+				if (option && option->data[4] != 0) {
+					/* return to init state */
+					bb_info_msg("Received DHCP NAK (%u)", option->data[4]);
+					d6_run_script(&packet, "nak");
+					if (state != REQUESTING)
+						d6_run_script(NULL, "deconfig");
+					change_listen_mode(LISTEN_RAW);
+					sleep(3); /* avoid excessive network traffic */
+					state = INIT_SELECTING;
+					client_config.first_secs = 0; /* make secs field count from 0 */
+					requested_ipv6 = NULL;
+					timeout = 0;
+					packet_num = 0;
+					already_waited_sec = 0;
+					continue;
+				}
+				option = d6_copy_option(packet.d6_options, packet_end, D6_OPT_SERVERID);
+				if (!option) {
+					bb_error_msg("no server ID, ignoring packet");
+					continue;
+					/* still selecting - this server looks bad */
+				}
+//Note: we do not bother comparing server IDs in Advertise and Reply msgs.
+//server_id variable is used solely for creation of proper server_id option
+//in outgoing packets. (why DHCPv6 even introduced it is a mystery).
+				free(client6_data.server_id);
+				client6_data.server_id = option;
+				if (packet.d6_msg_type == D6_MSG_ADVERTISE) {
+					/* enter requesting state */
+					state = REQUESTING;
+					timeout = 0;
+					packet_num = 0;
+					already_waited_sec = 0;
+					continue;
+				}
+				/* It's a D6_MSG_REPLY */
+/*
+ * RFC 3315 18.1.8. Receipt of Reply Messages
+ *
+ * Upon the receipt of a valid Reply message in response to a Solicit
+ * (with a Rapid Commit option), Request, Confirm, Renew, Rebind or
+ * Information-request message, the client extracts the configuration
+ * information contained in the Reply.  The client MAY choose to report
+ * any status code or message from the status code option in the Reply
+ * message.
+ *
+ * The client SHOULD perform duplicate address detection [17] on each of
+ * the addresses in any IAs it receives in the Reply message before
+ * using that address for traffic.  If any of the addresses are found to
+ * be in use on the link, the client sends a Decline message to the
+ * server as described in section 18.1.7.
+ *
+ * If the Reply was received in response to a Solicit (with a Rapid
+ * Commit option), Request, Renew or Rebind message, the client updates
+ * the information it has recorded about IAs from the IA options
+ * contained in the Reply message:
+ *
+ * -  Record T1 and T2 times.
+ *
+ * -  Add any new addresses in the IA option to the IA as recorded by
+ *    the client.
+ *
+ * -  Update lifetimes for any addresses in the IA option that the
+ *    client already has recorded in the IA.
+ *
+ * -  Discard any addresses from the IA, as recorded by the client, that
+ *    have a valid lifetime of 0 in the IA Address option.
+ *
+ * -  Leave unchanged any information about addresses the client has
+ *    recorded in the IA but that were not included in the IA from the
+ *    server.
+ *
+ * Management of the specific configuration information is detailed in
+ * the definition of each option in section 22.
+ *
+ * If the client receives a Reply message with a Status Code containing
+ * UnspecFail, the server is indicating that it was unable to process
+ * the message due to an unspecified failure condition.  If the client
+ * retransmits the original message to the same server to retry the
+ * desired operation, the client MUST limit the rate at which it
+ * retransmits the message and limit the duration of the time during
+ * which it retransmits the message.
+ *
+ * When the client receives a Reply message with a Status Code option
+ * with the value UseMulticast, the client records the receipt of the
+ * message and sends subsequent messages to the server through the
+ * interface on which the message was received using multicast.  The
+ * client resends the original message using multicast.
+ *
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |          OPTION_IA_NA         |          option-len           |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                        IAID (4 octets)                        |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                              T1                               |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                              T2                               |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                                                               |
+ * .                         IA_NA-options                         .
+ * .                                                               .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ *
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |          OPTION_IAADDR        |          option-len           |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                                                               |
+ * |                         IPv6 address                          |
+ * |                                                               |
+ * |                                                               |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                      preferred-lifetime                       |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                        valid-lifetime                         |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * .                                                               .
+ * .                        IAaddr-options                         .
+ * .                                                               .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+				free(client6_data.ia_na);
+				client6_data.ia_na = d6_copy_option(packet.d6_options, packet_end, D6_OPT_IA_NA);
+				if (!client6_data.ia_na) {
+					bb_error_msg("no lease time, ignoring packet");
+					continue;
+				}
+				if (client6_data.ia_na->len < (4 + 4 + 4) + (2 + 2 + 16 + 4 + 4)) {
+					bb_error_msg("IA_NA option is too short:%d bytes", client6_data.ia_na->len);
+					continue;
+				}
+				iaaddr = d6_find_option(client6_data.ia_na->data,
+						client6_data.ia_na->data + client6_data.ia_na->len,
+						D6_OPT_IAADDR
+				);
+				if (!iaaddr) {
+					bb_error_msg("no lease time, ignoring packet");
+					continue;
+				}
+				if (iaaddr->len < (16 + 4 + 4)) {
+					bb_error_msg("IAADDR option is too short:%d bytes", iaaddr->len);
+					continue;
+				}
+				/* Note: the address is sufficiently aligned for cast:
+				 * we _copied_ IA-NA, and copy is always well-aligned.
+				 */
+				requested_ipv6 = (struct in6_addr*) iaaddr->data;
+				move_from_unaligned32(lease_seconds, iaaddr->data + 16 + 4);
+				lease_seconds = ntohl(lease_seconds);
+				/* paranoia: must not be too small and not prone to overflows */
+				if (lease_seconds < 0x10)
+					lease_seconds = 0x10;
+/// TODO: check for 0 lease time?
+				if (lease_seconds >= 0x10000000)
+					lease_seconds = 0x0fffffff;
+				/* enter bound state */
+				timeout = lease_seconds / 2;
+				bb_info_msg("Lease obtained, lease time %u",
+					/*inet_ntoa(temp_addr),*/ (unsigned)lease_seconds);
+				d6_run_script(&packet, state == REQUESTING ? "bound" : "renew");
+
+				state = BOUND;
+				change_listen_mode(LISTEN_NONE);
+				if (opt & OPT_q) { /* quit after lease */
+					goto ret0;
+				}
+				/* future renew failures should not exit (JM) */
+				opt &= ~OPT_n;
+#if BB_MMU /* NOMMU case backgrounded earlier */
+				if (!(opt & OPT_f)) {
+					client_background();
+					/* do not background again! */
+					opt = ((opt & ~OPT_b) | OPT_f);
+				}
+#endif
+				already_waited_sec = 0;
+				continue; /* back to main loop */
+			}
+			continue;
+		/* case BOUND: - ignore all packets */
+		/* case RELEASED: - ignore all packets */
+		}
+		/* back to main loop */
+	} /* for (;;) - main loop ends */
+
+ ret0:
+	if (opt & OPT_R) /* release on quit */
+		perform_d6_release(&srv6_buf, requested_ipv6);
+	retval = 0;
+ ret:
+	/*if (client_config.pidfile) - remove_pidfile has its own check */
+		remove_pidfile(client_config.pidfile);
+	return retval;
+}
diff --git a/networking/udhcp/d6_packet.c b/networking/udhcp/d6_packet.c
new file mode 100644
index 0000000..3a1bb3d
--- /dev/null
+++ b/networking/udhcp/d6_packet.c
@@ -0,0 +1,168 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Copyright (C) 2011 Denys Vlasenko.
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+#include "common.h"
+#include "d6_common.h"
+#include "dhcpd.h"
+#include <netinet/in.h>
+#include <netinet/if_ether.h>
+#include <netpacket/packet.h>
+
+#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
+void FAST_FUNC d6_dump_packet(struct d6_packet *packet)
+{
+	if (dhcp_verbose < 2)
+		return;
+
+	bb_info_msg(
+		" xid %x"
+		, packet->d6_xid32
+	);
+	//*bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
+	//bb_info_msg(" chaddr %s", buf);
+}
+#endif
+
+int FAST_FUNC d6_recv_kernel_packet(struct in6_addr *peer_ipv6
+	UNUSED_PARAM
+	, struct d6_packet *packet, int fd)
+{
+	int bytes;
+
+	memset(packet, 0, sizeof(*packet));
+	bytes = safe_read(fd, packet, sizeof(*packet));
+	if (bytes < 0) {
+		log1("Packet read error, ignoring");
+		return bytes; /* returns -1 */
+	}
+
+	if (bytes < offsetof(struct d6_packet, d6_options)) {
+		bb_info_msg("Packet with bad magic, ignoring");
+		return -2;
+	}
+	log1("Received a packet");
+	d6_dump_packet(packet);
+
+	return bytes;
+}
+
+/* Construct a ipv6+udp header for a packet, send packet */
+int FAST_FUNC d6_send_raw_packet(
+		struct d6_packet *d6_pkt, unsigned d6_pkt_size,
+		struct in6_addr *src_ipv6, int source_port,
+		struct in6_addr *dst_ipv6, int dest_port, const uint8_t *dest_arp,
+		int ifindex)
+{
+	struct sockaddr_ll dest_sll;
+	struct ip6_udp_d6_packet packet;
+	int fd;
+	int result = -1;
+	const char *msg;
+
+	fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IPV6));
+	if (fd < 0) {
+		msg = "socket(%s)";
+		goto ret_msg;
+	}
+
+	memset(&dest_sll, 0, sizeof(dest_sll));
+	memset(&packet, 0, offsetof(struct ip6_udp_d6_packet, data));
+	packet.data = *d6_pkt; /* struct copy */
+
+	dest_sll.sll_family = AF_PACKET;
+	dest_sll.sll_protocol = htons(ETH_P_IPV6);
+	dest_sll.sll_ifindex = ifindex;
+	dest_sll.sll_halen = 6;
+	memcpy(dest_sll.sll_addr, dest_arp, 6);
+
+	if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
+		msg = "bind(%s)";
+		goto ret_close;
+	}
+
+	packet.ip6.ip6_vfc = (6 << 4); /* 4 bits version, top 4 bits of tclass */
+	if (src_ipv6)
+		packet.ip6.ip6_src = *src_ipv6; /* struct copy */
+	packet.ip6.ip6_dst = *dst_ipv6; /* struct copy */
+	packet.udp.source = htons(source_port);
+	packet.udp.dest = htons(dest_port);
+	/* size, excluding IP header: */
+	packet.udp.len = htons(sizeof(struct udphdr) + d6_pkt_size);
+	packet.ip6.ip6_plen = packet.udp.len;
+	/* UDP checksum skips first four bytes of IP header.
+	 * IPv6 'hop limit' field should be 0.
+	 * 'next header' field should be summed as if it is in a different
+	 * position, therefore we write its value into ip6_hlim:
+	 */
+	packet.ip6.ip6_hlim = IPPROTO_UDP;
+	packet.udp.check = inet_cksum((uint16_t *)&packet + 2,
+				offsetof(struct ip6_udp_d6_packet, data) - 4 + d6_pkt_size);
+	/* fix 'hop limit' and 'next header' after UDP checksumming */
+	packet.ip6.ip6_hlim = 8;
+	packet.ip6.ip6_nxt = IPPROTO_UDP;
+
+	d6_dump_packet(d6_pkt);
+	result = sendto(fd, &packet, offsetof(struct ip6_udp_d6_packet, data) + d6_pkt_size,
+			/*flags:*/ 0,
+			(struct sockaddr *) &dest_sll, sizeof(dest_sll)
+	);
+	msg = "sendto";
+ ret_close:
+	close(fd);
+	if (result < 0) {
+ ret_msg:
+		bb_perror_msg(msg, "PACKET");
+	}
+	return result;
+}
+
+/* Let the kernel do all the work for packet generation */
+int FAST_FUNC d6_send_kernel_packet(
+		struct d6_packet *d6_pkt, unsigned d6_pkt_size,
+		struct in6_addr *src_ipv6, int source_port,
+		struct in6_addr *dst_ipv6, int dest_port)
+{
+	struct sockaddr_in6 sa;
+	int fd;
+	int result = -1;
+	const char *msg;
+
+	fd = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+	if (fd < 0) {
+		msg = "socket(%s)";
+		goto ret_msg;
+	}
+	setsockopt_reuseaddr(fd);
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sin6_family = AF_INET6;
+	sa.sin6_port = htons(source_port);
+	sa.sin6_addr = *src_ipv6; /* struct copy */
+	if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
+		msg = "bind(%s)";
+		goto ret_close;
+	}
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sin6_family = AF_INET6;
+	sa.sin6_port = htons(dest_port);
+	sa.sin6_addr = *dst_ipv6; /* struct copy */
+	if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
+		msg = "connect";
+		goto ret_close;
+	}
+
+	d6_dump_packet(d6_pkt);
+	result = safe_write(fd, d6_pkt, d6_pkt_size);
+	msg = "write";
+ ret_close:
+	close(fd);
+	if (result < 0) {
+ ret_msg:
+		bb_perror_msg(msg, "UDP");
+	}
+	return result;
+}
diff --git a/networking/udhcp/d6_socket.c b/networking/udhcp/d6_socket.c
new file mode 100644
index 0000000..56f69f6
--- /dev/null
+++ b/networking/udhcp/d6_socket.c
@@ -0,0 +1,34 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Copyright (C) 2011 Denys Vlasenko.
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+#include "common.h"
+#include "d6_common.h"
+#include <net/if.h>
+
+int FAST_FUNC d6_listen_socket(int port, const char *inf)
+{
+	int fd;
+	struct sockaddr_in6 addr;
+
+	log1("Opening listen socket on *:%d %s", port, inf);
+	fd = xsocket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+
+	setsockopt_reuseaddr(fd);
+	if (setsockopt_broadcast(fd) == -1)
+		bb_perror_msg_and_die("SO_BROADCAST");
+
+	/* NB: bug 1032 says this doesn't work on ethernet aliases (ethN:M) */
+	if (setsockopt_bindtodevice(fd, inf))
+		xfunc_die(); /* warning is already printed */
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sin6_family = AF_INET6;
+	addr.sin6_port = htons(port);
+	/* addr.sin6_addr is all-zeros */
+	xbind(fd, (struct sockaddr *)&addr, sizeof(addr));
+
+	return fd;
+}