netdev - tc filter by source port and destination port strange offset

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAE_-sdmwbA-Otz1a__tQrTB7jT53b7j0PB2q7xPV6MYLrY5YGg@mail.gmail.com>
Date:   Thu, 20 Aug 2020 00:30:49 +0300
From:   Denis Gubin <denis.gubin@...il.com>
To:     netdev@...r.kernel.org
Subject: tc filter by source port and destination port strange offset

Dear colleagues,

There are filters.
Let's have a look on it.

Pretty mode showing:

tc -p filter show dev ens5 parent ffff:

filter protocol ip pref 49146 u32 chain 0
filter protocol ip pref 49146 u32 chain 0 fh 806: ht divisor 1
filter protocol ip pref 49146 u32 chain 0 fh 806::800 order 2048 key
ht 806 bkt 0 terminal flowid ??? not_in_hw
  match IP protocol 16
  match dport 8080

Normal  mode showing:

tc filter show dev ens5 parent ffff:


filter protocol ip pref 49146 u32 chain 0
filter protocol ip pref 49146 u32 chain 0 fh 806: ht divisor 1
filter protocol ip pref 49146 u32 chain 0 fh 806::800 order 2048 key
ht 806 bkt 0 terminal flowid ??? not_in_hw
  match 00100000/00ff0000 at 8
  match 00001f90/0000ffff at 20


The string  "match 00100000/00ff0000 at 8" looks like is correct since
offset up 8 byte from IP Header point is "ip protocol field"

But string "match 00001f90/0000ffff at 20" looks like strange, doens't it?
Since 20 bytes offset up is IP Header "options field ip".

Could somebody explain it to me?

-- 
Best regards,
Denis Gubin