From f4e9f26480ef56ec09a871abf552cd2baac6cb10 Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Thu, 15 Aug 2024 00:40:43 +0200 Subject: [PATCH] pasta: Disable neighbour solicitations on device up to prevent DAD 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 Reviewed-by: David Gibson --- pasta.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/pasta.c b/pasta.c index e8883bd..1142f03 100644 --- a/pasta.c +++ b/pasta.c @@ -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);