[Bug 210860] [pf] [ip6] Incorrect TCP checksums after rdr

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=210860

--- Comment #2 from Joao Vieira <vieira+fbsd at yubo.be> ---
Hello Kristof,

Thanks for replying. As you suggested, I tried with the following rules
(replacing ::1 with GUA):

table <forward_subnets> {2001:16d8:ee03::cafe:d00d/128,!::1}
rdr pass log on lo0 inet6 proto tcp to <forward_subnets> ->
2a03:b0c0:1:d0::42e:f001 port 12300
pass out log route-to lo0 inet6 proto tcp to <forward_subnets> keep state

but the problem persists. I tried ifconfig lo0 -lro -tso and ifconfig vtnet0
-lro -tso and after that I saw less checksum errors but still saw one on
pflog0. Nothing got to the application (nc -l 2a03:b0c0:1:d0::42e:f001 12300).

# tcpdump -n -e -ttt -i pflog0 -vvv
00:00:00.000000 rule 0..16777216/0(match): pass out on vtnet0: (flowlabel
0xc4cbb, hlim 64, next-header TCP (6) payload length: 40)
2a03:b0c0:1:d0::42e:f001.39668 > 2001:16d8:ee03::cafe:d00d.80: Flags [S], cksum
0x8fdc (incorrect -> 0x78fc), seq 2180195351, win 65535, options [mss
1440,nop,wscale 6,sackOK,TS val 10681721 ecr 0], length 0
00:00:00.000093 rule 0..16777216/0(match): rdr in on lo0: (flowlabel 0xc4cbb,
hlim 64, next-header TCP (6) payload length: 40) 2a03:b0c0:1:d0::42e:f001.39668
> 2a03:b0c0:1:d0::42e:f001.12300: Flags [S], cksum 0x3965 (correct), seq
2180195351, win 65535, options [mss 1440,nop,wscale 6,sackOK,TS val 10681721
ecr 0], length 0

# tcpdump -n -e -ttt -i lo0 -vvv
00:00:00.000000 AF IPv6 (28), length 84: (flowlabel 0xd1846, hlim 64,
next-header TCP (6) payload length: 40) 2a03:b0c0:1:d0::42e:f001.59007 >
2001:16d8:ee03::cafe:d00d.80: Flags [S], cksum 0x18ea (correct), seq 927681064,
win 65535, options [mss 1440,nop,wscale 6,sackOK,TS val 10630808 ecr 0], length
0
00:00:00.000125 AF IPv6 (28), length 84: (class 0x01, flowlabel 0x3450f, hlim
64, next-header TCP (6) payload length: 40) 2001:16d8:ee03::cafe:d00d.80 >
2a03:b0c0:1:d0::42e:f001.59007: Flags [S.], cksum 0xb883 (correct), seq
3088270607, ack 927681065, win 65535, options [mss 1440,nop,wscale 6,sackOK,TS
val 3250889069 ecr 10630808], length 0
00:00:03.022264 AF IPv6 (28), length 84: (class 0x0b, flowlabel 0x3450f, hlim
64, next-header TCP (6) payload length: 40) 2001:16d8:ee03::cafe:d00d.80 >
2a03:b0c0:1:d0::42e:f001.59007: Flags [S.], cksum 0xb883 (correct), seq
3088270607, ack 927681065, win 65535, options [mss 1440,nop,wscale 6,sackOK,TS
val 3250889069 ecr 10630808], length 0
00:00:00.000108 AF IPv6 (28), length 64: (hlim 64, next-header TCP (6) payload
length: 20) 2a03:b0c0:1:d0::42e:f001.59007 > 2001:16d8:ee03::cafe:d00d.80:
Flags [R], cksum 0xb7ee (correct), seq 927681065, win 0, length 0

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