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ndp: Fix Clang analyzer warning (clang-analyzer-security.PointerSub)

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Addresses Clang warning: "Subtraction of two pointers that do not
point into the same array is undefined behavior" for the line:
  `ndp_send(c, dst, &ra, ptr - (unsigned char *)&ra);`

Here, `ptr` is `&ra.var[0]`. The subtraction calculates the offset
of `var[0]` within the `struct ra_options ra`. Since `ptr` points
inside `ra`, this pointer arithmetic is well-defined for
calculating the size of the data to send, even if `ptr` and `&ra`
are not strictly considered part of the same "array" by the analyzer.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
Laurent Vivier 2025-05-13 11:41:01 +02:00 • committed by Stefano Brivio
parent a6b9832e49
commit 0f7bf10b0a
1 changed files with 1 additions and 0 deletions

1
ndp.c
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@ -328,6 +328,7 @@ static void ndp_ra(const struct ctx *c, const struct in6_addr *dst)
memcpy(&ra.source_ll.mac, c->our_tap_mac, ETH_ALEN);
/* NOLINTNEXTLINE(clang-analyzer-security.PointerSub) */
ndp_send(c, dst, &ra, ptr - (unsigned char *)&ra);
}