[Bug 224730] ipfw dyn_keepalive sends a strange packet

bugzilla-noreply at freebsd.org bugzilla-noreply at freebsd.org
Sat Dec 30 14:42:21 UTC 2017


https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=224730

            Bug ID: 224730
           Summary: ipfw dyn_keepalive sends a strange packet
           Product: Base System
           Version: 10.3-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: hossy-fbsd at hossy.flnet.org

reproduce process:
1. install FreeBSD 10.3-R
2. enable ipfw
# kldload ipfw
# ipfw add 10 pass tcp from any to any 25 setup keep-state
3. dump loopback packets
# tcpdump -i lo0 tcp
4. connect to sendmail
# telnet localhost 25
5. wait about 5min.

tcpdump's log:
16:06:42.945550 IP6 client.example.net.61971 > server.example.net.ldap: Flags
[S], seq 4054001667, win 65535, options [mss 16324,nop,wscale 6,sackOK,TS val
2061573 ecr 0], length 0
16:06:42.945573 IP6 server.example.net.ldap > client.example.net.61971: Flags
[S.], seq 1721556881, ack 4054001668, win 65535, options [mss 16324,nop,wscale
6,sackOK,TS val 2786106269 ecr 2061573], length 0
16:06:42.945610 IP6 client.example.net.61971 > server.example.net.ldap: Flags
[.], ack 1, win 1274, options [nop,nop,TS val 2061573 ecr 2786106269], length 0
16:06:42.945679 IP6 client.example.net.61971 > server.example.net.ldap: Flags
[P.], seq 1:15, ack 1, win 1274, options [nop,nop,TS val 2061573 ecr
2786106269], length 14
16:06:42.945978 IP6 server.example.net.ldap > client.example.net.61971: Flags
[P.], seq 1:15, ack 15, win 1274, options [nop,nop,TS val 2786106269 ecr
2061573], length 14
16:06:42.946094 IP6 client.example.net.61971 > server.example.net.ldap: Flags
[P.], seq 15:108, ack 15, win 1274, options [nop,nop,TS val 2061573 ecr
2786106269], length 93
16:06:42.946340 IP6 server.example.net.ldap > client.example.net.61971: Flags
[P.], seq 15:29, ack 108, win 1274, options [nop,nop,TS val 2786106269 ecr
2061573], length 14
16:06:42.946764 IP6 client.example.net.61971 > server.example.net.ldap: Flags
[P.], seq 108:255, ack 29, win 1274, options [nop,nop,TS val 2061574 ecr
2786106269], length 147
16:06:42.947396 IP6 server.example.net.ldap > client.example.net.61971: Flags
[P.], seq 29:80, ack 255, win 1274, options [nop,nop,TS val 2786106270 ecr
2061574], length 51
16:06:43.047712 IP6 client.example.net.61971 > server.example.net.ldap: Flags
[.], ack 80, win 1274, options [nop,nop,TS val 2061675 ecr 2786106270], length
0
16:11:24.660499 IP6 client.example.net.61971 > server.example.net.ldap: Flags
[.], ack 80, win 0, length 0
16:11:24.660609 IP6 server.example.net.ldap > client.example.net.61971: Flags
[.], ack 255, win 1274, options [nop,nop,TS val 2786387984 ecr 2061675], length
0

l.11 [win 0, length 0] packet is strange.

1. why `win' is 0?
2. why it doesn't have timestamp?

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