netlink: specs: tcp_metrics: fix the attribute length checks

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TCP_FASTOPEN_COOKIE_MAX is the longest cookie we accept, not the shortest
one. Cookies are even sized, from 4 bytes up, and the ones Linux itself
generates are 8 bytes, so a 16 byte minimum declares all but the longest
cookie invalid. The reference policy kept under #if 0 in tcp_metrics.c
spells it as a maximum, which is what .len means for NLA_BINARY.

The IPv6 addresses err the other way. The policy uses
NLA_POLICY_EXACT_LEN() for both, so a request carrying a longer address is
rejected with -ERANGE, even though the spec advertises 16 bytes as a mere
minimum. Were the policy generated from this spec, as kernel-policy: global
promises, the check would turn into NLA_POLICY_MIN_LEN() and start
accepting over-long addresses, of which nla_get_in6_addr() would take the
first 16 bytes.

Nothing generated changes. fopen-cookie is reply-only so it never gets a
policy entry, and exact-len only feeds the policy (and the fixed size array
form, which needs a sub-type).

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>
Link: https://patch.msgid.link/20260912234337.308298-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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Jakub Kicinski 2026-09-12 16:43:36 -07:00 • committed by Paolo Abeni

parent e8c06b8952

commit 4358a3e8e7

1 changed files with 3 additions and 3 deletions

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Documentation/netlink/specs/tcp_metrics.yaml

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