Trouble with IPFW or TCP?
Ivan Voras
ivoras at freebsd.org
Thu Apr 3 23:34:36 UTC 2008
In which case would an ipfw ruleset like this:
00100 114872026 40487887607 allow ip from any to any via lo0
00200 0 0 deny ip from any to 127.0.0.0/8
00300 0 0 deny ip from 127.0.0.0/8 to any
00600 1585 112576 deny ip from table(0) to me
01000 90279 7325972 allow icmp from any to any
05000 475961039 334422494257 allow tcp from me to any setup keep-state
05100 634155 65779377 allow udp from me to any keep-state
06022 409604 69177326 allow tcp from any to me dst-port 22 setup
keep-state
06080 52159025 43182548092 allow tcp from any to me dst-port 80 setup
keep-state
06443 6392366 2043532158 allow tcp from any to me dst-port 443 setup
keep-state
07020 517065 292377553 allow tcp from any to me dst-port 8080
setup keep-state
65400 12273387 629703212 deny log ip from any to any
65535 0 0 deny ip from any to any
Generate syslog messages like these:
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:60725
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:57387
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:57387
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:61998
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:61998
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:64288
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:64288
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:50212
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:50212
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:58149
my.ip.my.ip:443 in via em0
Apr 4 01:02:06 my.ip kernel: ipfw: 65400 Deny TCP xx.xx.xx.xx:58149
my.ip.my.ip:443 in via em0
Apr 4 01:02:13 my.ip kernel: ipfw: 65400 Deny TCP yy.yy.yy.yy:61919
my.ip.my.ip:443 in via em0
Apr 4 01:02:13 my.ip kernel: ipfw: 65400 Deny TCP yy.yy.yy.yy:61919
my.ip.my.ip:443 in via em0
Apr 4 01:02:13 my.ip kernel: ipfw: 65400 Deny TCP yy.yy.yy.yy:56792
my.ip.my.ip:443 in via em0
Apr 4 01:02:13 my.ip kernel: ipfw: 65400 Deny TCP yy.yy.yy.yy:56792
my.ip.my.ip:443 in via em0
Apr 4 01:02:14 my.ip kernel: ipfw: 65400 Deny TCP yy.yy.yy.yy:53795
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:58314
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:63204
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:58314
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:52125
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:53386
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:63626
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:63204
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:51376
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:61880
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:49319
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:52125
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:62381
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:53386
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:63626
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:51376
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:54109
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:56945
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:61880
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:50800
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:49319
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:53347
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:58735
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:58732
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:62381
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:56837
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:54109
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:65318
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:56945
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:50800
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:53347
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:58735
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:58732
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:56837
my.ip.my.ip:443 in via em0
Apr 4 01:02:16 my.ip kernel: ipfw: 65400 Deny TCP zz.zz.zz.zz:65318
my.ip.my.ip:443 in via em0
?
I can connect with plain telnet from the reported addresses without
problems. One thing that is suspicious is that the messages come in
these bursts (which I can't explain) but the Apache's listen backlog
should handle those. In any case, I don't think they are connection
requests:
Here's output of "tcpdump -v host xx.xx.xx.xx and port 443":
01:13:07.654677 IP (tos 0x0, ttl 58, id 54089, offset 0, flags [none],
proto TCP (6), length 40) xx.xx.xx.xx.58789 > my.ip.my.ip.https: .,
cksum 0x54ca (correct), ack 3708282724 win 0
01:13:07.654764 IP (tos 0x0, ttl 58, id 54095, offset 0, flags [none],
proto TCP (6), length 40) xx.xx.xx.xx.61579 > my.ip.my.ip.https: .,
cksum 0xf60d (correct), ack 610863831 win 0
01:13:07.654810 IP (tos 0x0, ttl 58, id 54099, offset 0, flags [none],
proto TCP (6), length 40) xx.xx.xx.xx.61852 > my.ip.my.ip.https: .,
cksum 0xab18 (correct), ack 1491048554 win 0
01:13:07.654854 IP (tos 0x0, ttl 58, id 54103, offset 0, flags [none],
proto TCP (6), length 40) xx.xx.xx.xx.63950 > my.ip.my.ip.https: .,
cksum 0x1e51 (correct), ack 2955921131 win 0
01:13:07.654897 IP (tos 0x0, ttl 58, id 54107, offset 0, flags [none],
proto TCP (6), length 40) xx.xx.xx.xx.53299 > my.ip.my.ip.https: .,
cksum 0xa141 (correct), ack 2339864417 win 0
01:13:07.654940 IP (tos 0x0, ttl 58, id 54121, offset 0, flags [none],
proto TCP (6), length 40) xx.xx.xx.xx.50521 > my.ip.my.ip.https: .,
cksum 0x2c55 (correct), ack 216576745 win 0
01:13:07.654984 IP (tos 0x0, ttl 58, id 54123, offset 0, flags [DF],
proto TCP (6), length 52) xx.xx.xx.xx.58789 > my.ip.my.ip.https: .,
cksum 0x882d (correct), ack 1 win 33304 <nop,nop,timestamp 140692997
4077078528>
01:13:07.655026 IP (tos 0x0, ttl 58, id 54126, offset 0, flags [DF],
proto TCP (6), length 52) xx.xx.xx.xx.61579 > my.ip.my.ip.https: .,
cksum 0x0617 (correct), ack 1 win 33304 <nop,nop,timestamp 140692997
3172245833>
01:13:07.655069 IP (tos 0x0, ttl 58, id 54128, offset 0, flags [DF],
proto TCP (6), length 52) xx.xx.xx.xx.61852 > my.ip.my.ip.https: .,
cksum 0x7006 (correct), ack 1 win 33304 <nop,nop,timestamp 140692997
3472415360>
01:13:07.655112 IP (tos 0x0, ttl 58, id 54130, offset 0, flags [DF],
proto TCP (6), length 52) xx.xx.xx.xx.63950 > my.ip.my.ip.https: .,
cksum 0x7ade (correct), ack 1 win 33304 <nop,nop,timestamp 140692997
415365400>
01:13:07.655155 IP (tos 0x0, ttl 58, id 54132, offset 0, flags [DF],
proto TCP (6), length 52) xx.xx.xx.xx.53299 > my.ip.my.ip.https: .,
cksum 0x4087 (correct), ack 1 win 33304 <nop,nop,timestamp 140692997
2999393370>
01:13:07.655197 IP (tos 0x0, ttl 58, id 54139, offset 0, flags [DF],
proto TCP (6), length 52) xx.xx.xx.xx.50521 > my.ip.my.ip.https: .,
cksum 0x13e0 (correct), ack 1 win 33304 <nop,nop,timestamp 140692997
3427580559>
There are no SYNs here, so it looks to me like something mid-traffic.
For addresses such as those in the ipfw log, I see several messages like:
Mar 24 17:00:01 my.ip kernel: TCP: [xx.xx.xx.xx]:64714 to
[my.ip.my.ip]:443 tcpflags 0x18<PUSH,ACK>; tcp_do_segment: FIN_WAIT_2:
Received 198 bytes of data after socket was closed, sending RST and
removing tcpcb
Mar 24 17:10:57 my.ip kernel: 6110>ipfw: 65400 Deny TCP
xx.xx.xx.xx:58213 my.ip.my.ip:443 in via em0
Mar 25 00:00:05 my.ip kernel: TCP: [xx.xx.xx.xx]:52233 to
[my.ip.my.ip]:443 tcpflags 0x10<ACK>; syncache_expand: Segment failed
SYNCOOKIE authentication, segment rejected (probably spoofed)
Mar 25 01:45:05 my.ip kernel: TCP: [xx.xx.xx.xx]:51120 to
[my.ip.my.ip]:443 tcpflags 0x10<ACK>; syncache_expand: Segment failed
SYNCOOKIE authentication, segment rejected (probably spoofed)
Mar 25 01:45:05 my.ip kernel: TCP: [xx.xx.xx.xx]:51120 to
[my.ip.my.ip]:443 tcpflags 0x10<ACK>; syncache_expand: Segment failed
SYNCOOKIE authentication, segment rejected (probably spoofed)
Mar 25 14:00:09 my.ip kernel: TCP: [xx.xx.xx.xx]:55665 to
[my.ip.my.ip]:443 tcpflags 0x10<ACK>; syncache_expand: Segment failed
SYNCOOKIE authentication, segment rejected (probably spoofed)
Mar 25 14:00:09 my.ip kernel: TCP: [xx.xx.xx.xx]:55665 to
[my.ip.my.ip]:443 tcpflags 0x10<ACK>; syncache_expand: Segment failed
SYNCOOKIE authentication, segment rejected (probably spoofed)
Mar 25 17:00:00 my.ip kernel: TCP: [xx.xx.xx.xx]:60048 to
[my.ip.my.ip]:443 tcpflags 0x18<PUSH,ACK>; tcp_do_segment: FIN_WAIT_1:
Received 346 bytes of data after socket was closed, sending RST and
removing tcpcb
Mar 25 17:00:00 my.ip kernel: TCP: [xx.xx.xx.xx]:60048 to
[my.ip.my.ip]:443 tcpflags 0x11<FIN,ACK>; syncache_expand: Segment
failed SYNCOOKIE authentication, segment rejected (probably spoofed)
Mar 25 23:00:01 my.ip kernel: TCP: [xx.xx.xx.xx]:50205 to
[my.ip.my.ip]:443 tcpflags 0x18<PUSH,ACK>; tcp_do_segment: FIN_WAIT_1:
Received 346 bytes of data after socket was closed, sending RST and
removing tcpcb
Mar 25 23:00:01 my.ip kernel: TCP: [xx.xx.xx.xx]:50205 to
[my.ip.my.ip]:443 tcpflags 0x11<FIN,ACK>; syncache_expand: Segment
failed SYNCOOKIE authentication, segment rejected (probably spoofed)
Mar 26 00:38:49 my.ip kernel: <a10>ipfw: 65400 Deny TCP
xx.xx.xx.xx:61129 my.ip.my.ip:443 in via em0
Apr 2 09:00:01 my.ip kernel: TCP: [xx.xx.xx.xx]:57248 to
[my.ip.my.ip]:443 tcpflags 0x18<PUSH,ACK>; tcp_do_segment: FIN_WAIT_1:
Received 330 bytes of data after socket was closed, sending RST and
removing tcpcb
Apr 2 09:00:01 my.ip kernel: TCP: [xx.xx.xx.xx]:57248 to
[my.ip.my.ip]:443 tcpflags 0x11<FIN,ACK>; syncache_expand: Segment
failed SYNCOOKIE authentication, segment rejected (probably spoofed)
But these messages do *not* occur when the ipfw log and tcpdump record
the above described behaviour so it might not be connected.
The machine at my.ip is running 7.0-RELEASE i386, the rest are a set of
machines that send trivial periodic (every 15 minutes) HTTPS messages to
this machine.
In this set most are 6.2 or 6.3, mixed i386 and amd64. The one 7-STABLE
machine that does the same thing doesn't generate the behaviour
described above so it might be something specific to when 6.x machines
talk to 7.x. Was there a bug like that in 6.x?
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