udhcpc: add support for DHCP option 212 (RFC 5969)

The patch is from OpenWRT people.

function                                             old     new   delta
xmalloc_optname_optval                               637     874    +237
dhcp_option_strings                                  237     243      +6
dhcp_optflags                                         68      70      +2
len_of_option_as_string                               12      13      +1
dhcp_option_lengths                                   12      13      +1
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/0 up/down: 247/0)             Total: 247 bytes

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

3 files changed, 82 insertions, 2 deletions

diff --git a/networking/udhcp/common.c b/networking/udhcp/common.c
index 70e3461..ba41905 100644
--- a/networking/udhcp/common.c
+++ b/networking/udhcp/common.c
@@ -59,6 +59,7 @@ const struct dhcp_optflag dhcp_optflags[] = {
 	{ OPTION_U16                              , 0x84 }, /* DHCP_VLAN_ID       */
 	{ OPTION_U8                               , 0x85 }, /* DHCP_VLAN_PRIORITY */
 #endif
+	{ OPTION_6RD                              , 0xd4 }, /* DHCP_6RD           */
 	{ OPTION_STATIC_ROUTES                    , 0xf9 }, /* DHCP_MS_STATIC_ROUTES */
 	{ OPTION_STRING                           , 0xfc }, /* DHCP_WPAD          */
 
@@ -126,6 +127,7 @@ const char dhcp_option_strings[] ALIGN1 =
 	"vlanid" "\0"      /* DHCP_VLAN_ID        */
 	"vlanpriority" "\0"/* DHCP_VLAN_PRIORITY  */
 #endif
+	"ip6rd" "\0"       /* DHCP_6RD            */
 	"msstaticroutes""\0"/* DHCP_MS_STATIC_ROUTES */
 	"wpad" "\0"        /* DHCP_WPAD           */
 	;
@@ -154,6 +156,7 @@ const uint8_t dhcp_option_lengths[] ALIGN1 = {
 	[OPTION_S32] =     4,
 	/* Just like OPTION_STRING, we use minimum length here */
 	[OPTION_STATIC_ROUTES] = 5,
+	[OPTION_6RD] =    22,  /* ignored by udhcp_str2optset */
 };
 
 
diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index 7862668..da0bd38 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -88,6 +88,7 @@ enum {
 	OPTION_S32,
 	OPTION_BIN,
 	OPTION_STATIC_ROUTES,
+	OPTION_6RD,
 #if ENABLE_FEATURE_UDHCP_RFC3397
 	OPTION_DNS_STRING,  /* RFC1035 compressed domain name list */
 	OPTION_SIP_SERVERS,
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index ddfe3cc..311d486 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -100,6 +100,7 @@ static const uint8_t len_of_option_as_string[] = {
 	[OPTION_IP              ] = sizeof("255.255.255.255 "),
 	[OPTION_IP_PAIR         ] = sizeof("255.255.255.255 ") * 2,
 	[OPTION_STATIC_ROUTES   ] = sizeof("255.255.255.255/32 255.255.255.255 "),
+	[OPTION_6RD             ] = sizeof("32 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
 	[OPTION_STRING          ] = 1,
 #if ENABLE_FEATURE_UDHCP_RFC3397
 	[OPTION_DNS_STRING      ] = 1, /* unused */
@@ -123,6 +124,24 @@ static int sprint_nip(char *dest, const char *pre, const uint8_t *ip)
 	return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]);
 }
 
+static int sprint_nip6(char *dest, const char *pre, const uint8_t *ip)
+{
+	char hexstrbuf[16 * 2];
+	bin2hex(hexstrbuf, (void*)ip, 16);
+	return sprintf(dest, "%s"
+		"%.4s:%.4s:%.4s:%.4s:%.4s:%.4s:%.4s:%.4s",
+		pre,
+		hexstrbuf + 0 * 4,
+		hexstrbuf + 1 * 4,
+		hexstrbuf + 2 * 4,
+		hexstrbuf + 3 * 4,
+		hexstrbuf + 4 * 4,
+		hexstrbuf + 5 * 4,
+		hexstrbuf + 6 * 4,
+		hexstrbuf + 7 * 4
+	);
+}
+
 /* really simple implementation, just count the bits */
 static int mton(uint32_t mask)
 {
@@ -147,7 +166,8 @@ static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_
 
 	type = optflag->flags & OPTION_TYPE_MASK;
 	optlen = dhcp_option_lengths[type];
-	upper_length = len_of_option_as_string[type] * ((unsigned)len / (unsigned)optlen);
+	upper_length = len_of_option_as_string[type]
+		* ((unsigned)(len + optlen - 1) / (unsigned)optlen);
 
 	dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
 	dest += sprintf(ret, "%s=", opt_name);
@@ -232,6 +252,62 @@ static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_
 
 			return ret;
 		}
+		case OPTION_6RD: {
+			/* Option binary format (see RFC 5969):
+			 * 0                   1                   2                   3
+			 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+			 * |  OPTION_6RD   | option-length |  IPv4MaskLen  |  6rdPrefixLen |
+			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+			 * |                                                               |
+			 * |                           6rdPrefix                           |
+			 * |                          (16 octets)                          |
+			 * |                                                               |
+			 * |                                                               |
+			 * |                                                               |
+			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+			 * |                     6rdBRIPv4Address(es)                      |
+			 * .                                                               .
+			 * .                                                               .
+			 * .                                                               .
+			 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+			 *
+			 * We convert it to a string
+			 * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..."
+			 */
+
+			/* Sanity check: ensure that our length is at least 22 bytes, that
+			 * IPv4MaskLen <= 32,
+			 * 6rdPrefixLen <= 128,
+			 * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128
+			 * (2nd condition need no check - it follows from 1st and 3rd).
+			 * If any of these requirements is not fulfilled, return with empty
+			 * value.
+			 */
+			if (len >= 22
+			 && option[0] <= 32
+			 && (option[1] + 32 - option[0]) <= 128
+			) {
+				/* IPv4MaskLen */
+				dest += sprintf(dest, "%u ", *option++);
+				/* 6rdPrefixLen */
+				dest += sprintf(dest, "%u ", *option++);
+				/* 6rdPrefix */
+				dest += sprint_nip6(dest, "", option);
+				option += 16;
+				len -= 1 + 1 + 16;
+				/* 6rdBRIPv4Address(es) */
+				while (1) {
+					dest += sprint_nip(dest, " ", option);
+					option += 4;
+					len -= 4;
+					if (len < 0)
+						break;
+				}
+			}
+
+			return ret;
+		}
 #if ENABLE_FEATURE_UDHCP_RFC3397
 		case OPTION_DNS_STRING:
 			/* unpack option into dest; use ret for prefix (i.e., "optname=") */
@@ -394,7 +470,7 @@ static char **fill_envp(struct dhcp_packet *packet)
 			len = temp[-OPT_DATA + OPT_LEN];
 			*curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
 			ofs = sprintf(*curr, "opt%u=", i);
-			bin2hex(*curr + ofs, (void*) temp, len)[0] = '\0';
+			*bin2hex(*curr + ofs, (void*) temp, len) = '\0';
 			putenv(*curr++);
 		}
 		i++;