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udp: Reduce scope of rport in udp_invert_portmap()

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cppcheck 2.14 warns that the scope of the rport variable could be
reduced: do that, as reverted commit c80fa6a6bb ("udp: Make rport
calculation more local") did, but keep the temporary variable of
in_port_t type, otherwise the sum gets promoted to int.

While at it, add a comment explaining why we calculate rport like
this instead of directly using the sum as array index.

Reported-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Stefano Brivio 2024-06-21 15:21:26 +02:00
parent 054697598f
commit 1ee2ecade3
1 changed files with 10 additions and 2 deletions
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12
udp.c
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@ -279,10 +279,18 @@ static void udp_invert_portmap(struct udp_fwd_ports *fwd)
"Forward and reverse delta arrays must have same size");
for (i = 0; i < ARRAY_SIZE(fwd->f.delta); i++) {
in_port_t delta = fwd->f.delta[i];
in_port_t rport = i + delta;
if (delta)
if (delta) {
/* Keep rport calculation separate from its usage: we
* need to perform the sum in in_port_t width (that is,
* modulo 65536), but C promotion rules would sum the
* two terms as 'int', if we just open-coded the array
* index as 'i + delta'.
*/
in_port_t rport = i + delta;
fwd->rdelta[rport] = NUM_PORTS - delta;
}
}
}