TCP ECN

[Oles Hnatkevych]

Hello dear All.

I have a very strange FreeBSD box. It was 4.6, now it runs currently 4.11 -
prerelease, cvsupped yesterday, on sunday. However the problem
persists.

The problem is that TCP connections to this BOX with SYN+ENC bits can
not be established. There's another Linux box, that can not send mail
to FreeBSD box. tcpdump shows the following:

12:12:21.960831 212.82.218.243.4349 > 212.109.60.114.25: SE 855427262:855427262(0) win 5840 <mss 1460,sackOK,timestamp 300064221 0,nop,wscale 0> (DF)
12:12:24.960902 212.82.218.243.4349 > 212.109.60.114.25: SE 855427262:855427262(0) win 5840 <mss 1460,sackOK,timestamp 300064521 0,nop,wscale 0> (DF)
12:12:30.957610 212.82.218.243.4349 > 212.109.60.114.25: SE 855427262:855427262(0) win 5840 <mss 1460,sackOK,timestamp 300065121 0,nop,wscale 0> (DF)
12:12:42.957429 212.82.218.243.4349 > 212.109.60.114.25: SE 855427262:855427262(0) win 5840 <mss 1460,sackOK,timestamp 300066321 0,nop,wscale 0> (DF)
12:13:06.955415 212.82.218.243.4349 > 212.109.60.114.25: SE 855427262:855427262(0) win 5840 <mss 1460,sackOK,timestamp 300068721 0,nop,wscale 0> (DF)

... and timeout.

Yet again, when remote administator uses telnet to connect to port 25,
everything goes as needed.

12:13:13.787333 212.82.218.243.50686 > 212.109.60.114.25: S 1250984054:1250984054(0) win 65535 <mss 1460,nop,wscale 1,nop,nop,timestamp 1124171 0> (DF)
12:13:13.823640 212.109.60.114.25 > 212.82.218.243.50686: S 1362670573:1362670573(0) ack 1250984055 win 57344 <mss 1460,nop,wscale 0,nop,nop,timestamp 6658994 1124171> (DF)
12:13:16.775253 212.82.218.243.50686 > 212.109.60.114.25: S 1250984054:1250984054(0) win 65535 <mss 1460,nop,wscale 1,nop,nop,timestamp 1124471 0> (DF)
12:13:16.813864 212.109.60.114.25 > 212.82.218.243.50686: S 1362670573:1362670573(0) ack 1250984055 win 57344 <mss 1460,nop,wscale 0,nop,nop,timestamp 6659293 1124471> (DF)

I have another FreeBSD boxes, they work properly in both cases, so
this is really an exceptional OS/kernel installation. I hardly believe
it is IPFW problem: the rule is

allow tcp from any to 212.109.60.114 25 in recv ${oif}

What the problem can be?????


-- 
 Oles                          mailto:don_oles at able.com.ua