diff options
| author | Beniamino Galvani <bgalvani@redhat.com> | 2022-05-27 21:16:18 +0100 |
|---|---|---|
| committer | Simon Kelley <simon@thekelleys.org.uk> | 2022-05-27 21:16:18 +0100 |
| commit | 770bce967cfc9967273d0acfb3ea018fb7b17522 (patch) | |
| tree | f4a6186b8e33db500dcb9ca8b6a04e3f0216b605 | |
| parent | a267a9e489ed824dbcf40ef857dfee55596e5405 (diff) | |
| download | dnsmasq-770bce967cfc9967273d0acfb3ea018fb7b17522.tar.gz | |
Fix parsing of IPv6 addresses with peer from netlink.
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))
| -rw-r--r-- | src/netlink.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/src/netlink.c b/src/netlink.c index da82943..c156cde 100644 --- a/src/netlink.c +++ b/src/netlink.c @@ -258,7 +258,16 @@ int iface_enumerate(int family, void *parm, int (*callback)()) while (RTA_OK(rta, len1)) { - if (rta->rta_type == IFA_ADDRESS) + /* + * Important comment: (from if_addr.h) + * IFA_ADDRESS is prefix address, rather than local interface address. + * It makes no difference for normally configured broadcast interfaces, + * but for point-to-point IFA_ADDRESS is DESTINATION address, + * local address is supplied in IFA_LOCAL attribute. + */ + 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) { |