[Bug 1775] New: RAW PAYLOAD EXPRESSION offset is limited to 2048

bugzilla-daemon at netfilter.org bugzilla-daemon at netfilter.org
Thu Sep 26 08:44:59 CEST 2024


https://bugzilla.netfilter.org/show_bug.cgi?id=1775

            Bug ID: 1775
           Summary: RAW PAYLOAD EXPRESSION offset is limited to 2048
           Product: nftables
           Version: 1.0.x
          Hardware: All
                OS: All
            Status: NEW
          Severity: critical
          Priority: P5
         Component: nft
          Assignee: pablo at netfilter.org
          Reporter: lev.shutov at gmail.com

RAW PAYLOAD EXPRESSION described here
https://manpages.debian.org/bookworm/nftables/nft.8.en.html#RAW_PAYLOAD_EXPRESSION

It has "offset" argument.

According to my tests it is limited to 2048.

--------------------------------------------------------------------------------
nft delete table raw-payload-test
nft add table raw-payload-test
nft add chain raw-payload-test input {type filter hook input priority filter\;}
nft add rule raw-payload-test input tcp dport 80 @ih,2047,8 1 log
nft add rule raw-payload-test input tcp dport 80 @ih,2048,8 2 log
--------------------------------------------------------------------------------

The 2nd rule throws error.

2048 bits is 256 bytes.
So RAW PAYLOAD EXPRESSION can be used only for the first 256 bytes of packet.

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