On Tue, Oct 24, 2017 at 09:58:48AM -0700, Jonathan Basseri 😶 wrote: > On Tue, Oct 24, 2017 at 12:04 AM, Steffen Klassert > <steffen.klass...@secunet.com> wrote: > > > > On Mon, Oct 23, 2017 at 06:18:55PM -0700, Jonathan Basseri wrote: > > > If a socket has a valid dst cache, then xfrm_lookup_route will get > > > skipped. However, the cache is not invalidated when applying policy to a > > > socket (i.e. IPV6_XFRM_POLICY). The result is that new policies are > > > sometimes ignored on those sockets. (Note: This was broken for IPv4 and > > > IPv6 at different times.) > > > > > > This can be demonstrated like so, > > > 1. Create UDP socket. > > > 2. connect() the socket. > > > 3. Apply an outbound XFRM policy to the socket. > > > 4. send() data on the socket. > > > > > > Packets will continue to be sent in the clear instead of matching an > > > xfrm or returning a no-match error (EAGAIN). This affects calls to > > > send() and not sendto(). > > > > > > Invalidating the sk_dst_cache is necessary to correctly apply xfrm > > > policies. Since we do this in xfrm_user_policy(), the sk_lock was > > > already acquired in either do_ip_setsockopt() or do_ipv6_setsockopt(), > > > and we may call __sk_dst_reset(). > > > > > > Performance impact should be negligible, since this code is only called > > > when changing xfrm policy, and only affects the socket in question. > > > > > > Note: Creating normal XFRM policies should have a similar effect on > > > sk_dst_cache entries that match the policy, but that is not fixed in > > > this patch. > > > > I think we don't have this problem with 'normal' policies. When > > inserting such a policy, we bump the IPv4/IPv6 genid. This should > > invalidate all cached dst entries, no? > > > That sounds reasonable to me. I had not confirmed the behavior for > normal policies, so I was trying to point out that this fix is only > for socket policies. Should I modify the commit message?
Yes, please do so. This comment may lead people to the wrong direction. Thanks!
