summaryrefslogtreecommitdiff
path: root/networking/udhcp/dhcpc.c
diff options
context:
space:
mode:
authorDenys Vlasenko2017-09-29 15:55:24 +0200
committerDenys Vlasenko2017-09-29 16:02:11 +0200
commita6a3ad327360669e0c12552f680382e3b9713489 (patch)
tree7dcfc65aa41e6f0f22e5b6631c35dbae8b99052f /networking/udhcp/dhcpc.c
parent2b9acc60c0468379cd24d13bc9e3f3e50761c0c9 (diff)
downloadbusybox-a6a3ad327360669e0c12552f680382e3b9713489.zip
busybox-a6a3ad327360669e0c12552f680382e3b9713489.tar.gz
udhcpc: paranoia when using kernel UDP mode for sending renew: server ID may be bogus
With new code, we request that target IP (server ID) must be directly reachable. If it's not, this happens: udhcpc: waiting 2000 seconds udhcpc: entering listen mode: kernel udhcpc: opening listen socket on *:68 wlan0 udhcpc: entering renew state udhcpc: sending renew to 1.1.1.1 udhcpc: send: Network is unreachable ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 1.1.1.1 needs routing, this is fishy! udhcpc: entering rebinding state udhcpc: entering listen mode: raw udhcpc: created raw socket udhcpc: sending renew to 0.0.0.0 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ going to use broadcast which is the desired behavior. Before the patch, packet to 1.1.1.1 was routed over eth0 (!) and maybe even into Internet (!!!). function old new delta udhcpc_main 2752 2763 +11 udhcp_send_kernel_packet 295 301 +6 send_renew 82 84 +2 send_packet 166 168 +2 bcast_or_ucast 23 25 +2 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 5/0 up/down: 23/0) Total: 23 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'networking/udhcp/dhcpc.c')
-rw-r--r--networking/udhcp/dhcpc.c34
1 files changed, 24 insertions, 10 deletions
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 6c74996..2ae8bcc 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -694,10 +694,16 @@ static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet, uint
static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
{
- if (server)
+ if (server) {
+ /* Without MSG_DONTROUTE, the packet was seen routed over
+ * _other interface_ if server ID is bogus (example: 1.1.1.1).
+ */
return udhcp_send_kernel_packet(packet,
ciaddr, CLIENT_PORT,
- server, SERVER_PORT);
+ server, SERVER_PORT,
+ /*send_flags: "to hosts only on directly connected networks" */ MSG_DONTROUTE
+ );
+ }
return raw_bcast_from_client_config_ifindex(packet, ciaddr);
}
@@ -735,7 +741,7 @@ static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
{
struct dhcp_packet packet;
- struct in_addr addr;
+ struct in_addr temp_addr;
/*
* RFC 2131 4.3.2 DHCPREQUEST message
@@ -766,8 +772,8 @@ static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requeste
*/
add_client_options(&packet);
- addr.s_addr = requested;
- bb_error_msg("sending select for %s", inet_ntoa(addr));
+ temp_addr.s_addr = requested;
+ bb_error_msg("sending select for %s", inet_ntoa(temp_addr));
return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
}
@@ -776,6 +782,7 @@ static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requeste
static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
{
struct dhcp_packet packet;
+ struct in_addr temp_addr;
/*
* RFC 2131 4.3.2 DHCPREQUEST message
@@ -806,7 +813,8 @@ static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
*/
add_client_options(&packet);
- bb_error_msg("sending %s", "renew");
+ temp_addr.s_addr = server;
+ bb_error_msg("sending renew to %s", inet_ntoa(temp_addr));
return bcast_or_ucast(&packet, ciaddr, server);
}
@@ -1524,11 +1532,17 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
* Anyway, it does recover by eventually failing through
* into INIT_SELECTING state.
*/
- send_renew(xid, server_addr, requested_ip);
- timeout >>= 1;
- continue;
+ if (send_renew(xid, server_addr, requested_ip) >= 0) {
+ timeout >>= 1;
+ continue;
+ }
+ /* else: error sending.
+ * example: ENETUNREACH seen with server
+ * which gave us bogus server ID 1.1.1.1
+ * which wasn't reachable (and probably did not exist).
+ */
}
- /* Timed out, enter rebinding state */
+ /* Timed out or error, enter rebinding state */
log1("entering rebinding state");
state = REBINDING;
/* fall right through */