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| author | Denys Vlasenko | 2011-10-20 14:47:41 +0200 |
|---|---|---|
| committer | Denys Vlasenko | 2011-10-20 14:47:41 +0200 |
| commit | 2af2acf9b516c378147ea678e4b3bec092e4e44d (patch) | |
| tree | 2eb45fc2b79b40c280da9200ef0434bccd88e0df | |
| parent | fbca0c68a75d0f2243bd7995d130e9cb8f6d2e18 (diff) | |
| download | busybox-2af2acf9b516c378147ea678e4b3bec092e4e44d.zip busybox-2af2acf9b516c378147ea678e4b3bec092e4e44d.tar.gz | |
udhcpc: add comment about server IP
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
| -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 36c8a3d..7cd0b7b 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"); |