diff options
| -rw-r--r-- | networking/udhcp/dhcpc.c | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c index 36c8a3dd3..7cd0b7bcb 100644 --- a/networking/udhcp/dhcpc.c +++ b/networking/udhcp/dhcpc.c @@ -1533,7 +1533,25 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv) case INIT_SELECTING: /* Must be a DHCPOFFER to one of our xid's */ if (*message == DHCPOFFER) { - /* TODO: why we don't just fetch server's IP from IP header? */ +/* What exactly is server's IP? There are several values. + * Example DHCP offer captured with tchdump: + * + * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src + * BOOTP fields: + * Your-IP 10.34.25.202 + * Server-IP 10.34.32.125 // "next server" IP + * Gateway-IP 10.34.25.254 // relay's address (if DHCP relays are in use) + * DHCP options: + * DHCP-Message Option 53, length 1: Offer + * Server-ID Option 54, length 4: 10.34.255.7 // "server ID" + * Default-Gateway Option 3, length 4: 10.34.25.254 // router + * + * We think that real server IP (one to use in renew/release) + * is one in Server-ID option. But I am not 100% sure. + * IP header's src and Gateway-IP (same in this exaqmple) + * might work too. + * "Next server" and router are definitely wrong ones to use, though... + */ temp = udhcp_get_option(&packet, DHCP_SERVER_ID); if (!temp) { bb_error_msg("no server ID, ignoring packet"); |