Reinaldo de Carvalho:
> Hi,
>
> Someone can tell me why EHLO reply send 2 packets?
>
> ~# postconf mail_version
> mail_version = 2.5.5
>
>
> ## tcpdump ##
>
> ^[OM^[OM15:41:23.546763 IP 10.15.10.9.49898 > 10.15.1.65.25: P 1:10(9)
> ack 34 win 46 <nop,nop,timestamp 927636169 259345475>
> e.....@.@.M.
> .
>
> ..A....`.[TU.s............
> 7J...uLCEHLO myhost.example.com
Above is "EHLO myhost.example.com" from the SMTP client to the SMTP server.
> 15:41:23.546924 IP 10.15.1.65.25 > 10.15.10.9.49898: . ack 10 win 91
> <nop,nop,timestamp 259346474 927636169>
> e.....@.?..9
> ..A
> .
> ....U.s.`.[]...[.......
> .uP*7J..
Above is a TCP acknowledgment from server kernel to client kernel.
> 15:41:23.547006 IP 10.15.1.65.25 > 10.15.10.9.49898: P 34:174(140) ack
> 10 win 91 <nop,nop,timestamp 259346474 927636169>
> e.....@.?...
> ..A
> .
> ....U.s.`.[]...[.J.....
> .uP*7J..250-server.example.com
> 250-PIPELINING
> 250-SIZE 26214400
> 250-AUTH PLAIN LOGIN
> 250-AUTH=PLAIN LOGIN
> 250-ENHANCEDSTATUSCODES
> 250 8BITMIME
Above is the SMTP server's response to the EHLO command.
> 15:41:23.547019 IP 10.15.10.9.49898 > 10.15.1.65.25: . ack 174 win 54
> <nop,nop,timestamp 927636169 259346474>
> e.....@.@.M.
> .
>
> ..A....`.[]U.t....6.......
> 7J...uP*
And that is a TCP acknowledgment from client kernel to server kernel.
Wietse
