The group address in the IGMP header is declared as uint16_t grpaddr[2],
so it decays to a pointer. Comparing it against INADDR_ANY compares the
address of a struct member against 0, which is always false. The General
Query branch is therefore unreachable and GCC discards it entirely.
Commit 09bb292fa2 ("net/igmp: fix build warning on GCC 12.2.0") replaced
the original
if (igmp->grpaddr == 0)
with
if (net_ipv4addr_cmp(igmp->grpaddr, INADDR_ANY) != 0)
but net_ipv4addr_cmp(a, b) expands to (a == b) and INADDR_ANY expands to
((in_addr_t)0), so the emitted comparison is unchanged. The -Waddress
diagnostic disappeared only because the comparison now originates inside
a macro expanded from a header included via -isystem, and GCC suppresses
warnings from system-header macros. The defect was hidden, not fixed.
That commit also rewrote the unicast query test from group->grpaddr != 0,
which was well-formed, into the same pointer comparison, making it
unconditionally true.
Convert the header field with net_ip4addr_conv32() once, and compare the
resulting in_addr_t. The conversion was already being done in the
group-specific branch, so this only hoists it and reuses it.
Impact: a General Query (destination 224.0.0.1, group address 0) is the
periodic query every IGMP querier sends. It currently falls through to
the group-specific branch, where igmp_grpallocfind() allocates a group
for 0.0.0.0 and schedules a report for it, while joined groups never have
their report timers restarted. The querier then ages out the membership
and multicast delivery to the device stops.
Signed-off-by: Jacob Dahl <dahl.jakejacob@gmail.com>
f20cf4aac3