kernel-xen-2.6.19-1.2898.2.3.fc7
dhclient-3.0.5-25.2.fc7

Basically, running dhclient in a Xen guest, dhclient is ignoring DHCP relies and
I'm seeing this in syslog:

Mar  7 12:11:29 localhost dhclient: 5 bad udp checksums in 5 packets

The background to this is that packets from Xen guests on the same host only
have partial checksums. (Not sure why)

In rh #219681, Herbert proposed a set of patches to fix this - first make the
TP_STATUS_CSUMNOTREADY flag available via recvmsg() auxdata and, second, make
dhclient check this flag and ignore the checksums if its set.

These patches aren't in rawhide, but I've tried applying the patches and it
seems dhclient isn't seeing the replies at all now - i.e. I'm seeing this in the
strace:

select(7, [5 6], [], [], {7, 996967})   = 0 (Timeout)
gettimeofday({1173356524, 521}, NULL)   = 0
time([1173356524])                      = 1173356524
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=3533, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=3533, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=3533, ...}) = 0
sendto(3, "<30>Mar  8 12:22:04 dhclient: DH"..., 89, MSG_NOSIGNAL, NULL, 0) = 89
write(2, "DHCPDISCOVER on eth0 to 255.255."..., 59) = 59
write(2, "\n", 1)                       = 1
write(6, "\377\377\377\377\377\377\0\26>l\5\0\10\0E\20\1H\0\0\0\0"..., 342) = 342
gettimeofday({1173356524, 1094}, NULL)  = 0
select(7, [5 6], [], [], {11, 998906})  = 0 (Timeout)



Attaching the patches as I've built them.