In the most common case, an IPv6 address doesn't have a peer and the IFA_ADDRESS netlink attribute contains the address itself.
But if the address has a peer (typically for point to point links), then IFA_ADDRESS contains the peer address and IFA_LOCAL contains the address [1]. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/net/ipv6/addrconf.c?h=v5.17#n5030 Fix the parsing of IPv6 addresses with peers, as currently dnsmasq unsuccessfully tries to bind on the peer address. A simple reproducer is: dnsmasq --conf-file=/dev/null -i dummy1 -d --bind-dynamic & sleep 2 ip link add dummy1 type dummy ip link set dummy1 up ip addr add dev dummy1 fd01::1/64 peer fd01::2/64 ip addr add dev dummy1 fd01::42/64 sleep 2 ss -lnp | grep dnsmasq | grep fd01 Before the patch: dnsmasq: failed to create listening socket for fd01::2: Cannot assign requested address dnsmasq: failed to create listening socket for fd01::2: Cannot assign requested address udp UNCONN 0 [fd01::42]:53 [::]:* users:(("dnsmasq",pid=23947,fd=14)) tcp LISTEN 0 [fd01::42]:53 [::]:* users:(("dnsmasq",pid=23947,fd=15 After: udp UNCONN 0 [fd01::42]:53 [::]:* users:(("dnsmasq",pid=23973,fd=16)) udp UNCONN 0 [fd01::1]:53 [::]:* users:(("dnsmasq",pid=23973,fd=14)) tcp LISTEN 0 [fd01::42]:53 [::]:* users:(("dnsmasq",pid=23973,fd=17)) tcp LISTEN 0 [fd01::1]:53 [::]:* users:(("dnsmasq",pid=23973,fd=15)) --- src/netlink.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/netlink.c b/src/netlink.c index da82943..a6d1972 100644 --- a/src/netlink.c +++ b/src/netlink.c @@ -258,7 +258,9 @@ int iface_enumerate(int family, void *parm, int (*callback)()) while (RTA_OK(rta, len1)) { - if (rta->rta_type == IFA_ADDRESS) + if (rta->rta_type == IFA_LOCAL) + addrp = ((struct in6_addr *)(rta+1)); + else if (rta->rta_type == IFA_ADDRESS && !addrp) addrp = ((struct in6_addr *)(rta+1)); else if (rta->rta_type == IFA_CACHEINFO) { -- 2.34.1 _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss
