From 1ee2ecade3f41e2a3e51c1e580b08cba977a7c8d Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Fri, 21 Jun 2024 15:21:26 +0200 Subject: [PATCH] udp: Reduce scope of rport in udp_invert_portmap() cppcheck 2.14 warns that the scope of the rport variable could be reduced: do that, as reverted commit c80fa6a6bb44 ("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 Signed-off-by: Stefano Brivio Reviewed-by: David Gibson --- udp.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/udp.c b/udp.c index 8181900..e089ef9 100644 --- a/udp.c +++ b/udp.c @@ -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; + } } }