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pasta: Disable neighbour solicitations on device up to prevent DAD

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As soon as we the kernel notifier for IPv6 address configuration
(addrconf_notify()) sees that we bring the target interface up
(NETDEV_UP), it will schedule duplicate address detection, so, by
itself, setting the nodad flag later is useless, because that won't
stop a detection that's already in progress.

However, if we disable neighbour solicitations with IFF_NOARP (which
is a misnomer for IPv6 interfaces, but there's no possibility of
mixing things up), the notifier will not trigger DAD, because it can't
be done, of course, without neighbour solicitations.

Set IFF_NOARP as we bring up the device, and drop it after we had a
chance to set the nodad attribute on the link.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Stefano Brivio 2024-08-15 00:40:43 +02:00
parent d6f0220731
commit f4e9f26480
1 changed files with 10 additions and 1 deletions
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11
pasta.c
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@ -303,10 +303,15 @@ void pasta_ns_conf(struct ctx *c)
strerror(-rc));
if (c->pasta_conf_ns) {
unsigned int flags = IFF_UP;
if (c->mtu != -1)
nl_link_set_mtu(nl_sock_ns, c->pasta_ifi, c->mtu);
nl_link_set_flags(nl_sock_ns, c->pasta_ifi, IFF_UP, IFF_UP);
if (c->ifi6) /* Avoid duplicate address detection on link up */
flags |= IFF_NOARP;
nl_link_set_flags(nl_sock_ns, c->pasta_ifi, flags, flags);
if (c->ifi4) {
if (c->ip4.no_copy_addrs) {
@ -353,6 +358,10 @@ void pasta_ns_conf(struct ctx *c)
strerror(-rc));
}
/* We dodged DAD: re-enable neighbour solicitations */
nl_link_set_flags(nl_sock_ns, c->pasta_ifi,
0, IFF_NOARP);
if (c->ip6.no_copy_addrs) {
rc = nl_addr_set(nl_sock_ns, c->pasta_ifi,
AF_INET6, &c->ip6.addr, 64);