nft: track each register individually
Instead of assuming only one register is used, track all 16 regs
individually.
This avoids need for the 'PREV_PAYLOAD' hack and also avoids the need to
clear out old flags:
When we see that register 'x' will be written to, that register state is
reset automatically.
Existing dissector decodes
ip saddr 1.2.3.4 meta l4proto tcp
... as
-s 6.0.0.0 -p tcp
iptables-nft -s 1.2.3.4 -p tcp is decoded correctly because the expressions
are ordered like:
meta l4proto tcp ip saddr 1.2.3.4
|
... and 'meta l4proto' did clear the PAYLOAD flag.
The simpler fix is:
ctx->flags &= ~NFT_XT_CTX_PAYLOAD;
in nft_parse_cmp(), but that breaks dissection of '1-42', because
the second compare ('cmp lte 42') will not find the
payload expression anymore.
Link: https://lore.kernel.org/netfilter-devel/20220922143544.GA22541@breakpoint.cc/T/#t
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Phil Sutter <phil@nwl.cc>
6 files changed
