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

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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