This example doesn't seem to work for me.
Does it work for anyone else out there?
$ iptables -A OUTPUT -m u32 --u32 "0>>22&0x3C@12>>26&0x3C@-3&0xFF=0:255"
-j LOG --log-prefix "TCP with payload *** "
I've tried some examples without the @ and they seem to be working but
I don't get anything in the log when I do this:
$ iptables -L OUTPUT -n -v
Chain OUTPUT (policy ACCEPT 17M packets, 1045M bytes)
pkts bytes target prot opt in out source
destination
0 0 LOG all -- * * 0.0.0.0/0
0.0.0.0/0 u32
0x0>>0x16&0x3c@0xc>>0x1a&0x3c@0xfffffffd&0xff=0x0:0xff LOG flags 0
level 4 prefix `TCP with payload *** '
(seems right)
$ tcpdump -lenX -i wlan0 -c 4
tcpdump: verbose output suppressed, use -v or -vv for full protocol
decode
listening on wlan0, link-type EN10MB (Ethernet), capture size 96 bytes
13:02:48.661944 00:21:6b:40:06:7e > 00:80:c8:b9:a4:2f, ethertype IPv4
(0x0800), length 114: 10.0.2.100.33306 > 66.166.0.98.ssh: P
3799762522:3799762570(48) ack 1707553806 win 1067 <nop,nop,timestamp
3419089842 694605510>
0x0000: 4510 0064 6a44 4000 4006 80d4 0a00 0264 E..djD@.@......d
0x0010: 42a6 0062 821a 0016 e27b c65a 65c7 340e B..b.....{.Ze.4.
0x0020: 8018 042b 90d1 0000 0101 080a cbcb 2bb2 ...+..........+.
0x0030: 2966 d6c6 c826 20cd 0b4c 0cf4 39cc 71e0 )f...&...L..9.q.
0x0040: ca4a 73c2 1058 d9e4 9cbd deec 0d10 f5f3 .Js..X..........
0x0050: 0d32 .2
...
several more packets that ought to show up in the log
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