Date: Thu, 30 Nov 2006 10:55:37 -0800 From: Luigi Rizzo <rizzo@icir.org> To: current@freebsd.org Subject: byte swapped udp length in diskless bootp request ? Message-ID: <20061130105537.A69725@xorpc.icir.org>
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i was just trying to diskless-boot a -current kernel,
and when it was time for the kernel to acquire the address
i was getting the usual
DHCP/BOOTP timeout for server 255.255.255.255
Usually it is because of lack of connectivity, but
a bit of inspection on the server showed (as you can see
below) that the UDP len field is byte-swapped - the 05bc
in the packet is in little-endian format, causing the
server to reject it.
I am trying to follow the code in sys/nfsclient/bootp_subr.c
(which should send the packet) but it seemd to call sosend()
(at line 755) to generate the packet, so it looks really strange
that the bug is in such a central place... any ideas ?
If that matters, the kernel is cross-compiled on a 6.2-RC1
box using a relatively fresh source tree.
cheers
luigi
TCPDUMP OUTPUT ON THE SERVER SIDE:
r1# tcpdump -nli em0 -s 0 -veX port 67
tcpdump: listening on em0, link-type EN10MB (Ethernet), capture size 65535 bytes
19:37:30.633525 00:40:f4:34:ad:09 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 1502: truncated-ip - 46645 bytes missing! (tos 0x0, ttl 1, id 83, offset 0, flags [none], proto: UDP (17), length: 48133, bad cksum 5bc (->fd95)!) 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 00:40:f4:34:ad:09, length: 48105, xid:0xffff0001, secs:400, flags: [Broadcast]
Client Ethernet Address: 00:40:f4:34:ad:09
Vendor-rfc1048:
MSZ:1460
VC:"FreeBSD:i386:7.0-CURRENT"
DHCP:DISCOVER
0x0000: 4500 bc05 0053 0000 0111 05bc 0000 0000 E....S..........
0x0010: ffff ffff 0044 0043 05bc 0000 0101 0600 .....D.C........
0x0020: ffff 0001 0190 8000 0000 0000 0000 0000 ................
0x0030: 0000 0000 0000 0000 0040 f434 ad09 0000 .........@.4....
... and so on. The rest of the packet has all
the good data up to
0x05a0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x05b0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0x05c0: 0000 0000 0000 0000 0000 0000 0000 0000 ................
----------------------------------------------------------
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