On Fri, Apr 04, 2025 at 01:01:45PM +0200, Stefano Brivio wrote:On Fri, 4 Apr 2025 11:57:58 +1100 David Gibson <david(a)gibson.dropbear.id.au> wrote:Ah.. yeah. When I wrote the above I didn't think I'd finish that series today :).On Fri, Apr 04, 2025 at 10:40:27AM +1100, David Gibson wrote:On the other hand, this patch applies cleanly on top of your "Use connect()ed sockets for both sides of UDP flows" series, and also semantically I couldn't spot any particular change or integration that we would need as a result in this patch.On Thu, Apr 03, 2025 at 06:27:06PM -0400, Jon Maloy wrote:Oh.. wait. I just realised this patch has a weird side effect, for flows which are initiated from outside, rather than from the guest. If the flow is initiated from outside, it's maybe a bit unlikely, but we could still get a non-default TTL from the guest on reply datagrams. That will trigger this code and alter the socket's TTL. But in this case the socket is not a flow specific socket, but the listening socket which initiated the flow, which could be handling packets on many flows. The "cached" TTL is stored per-flow, not per-socket, so we won't look at the right value when we process datagrams from other flows, so they may go out with the wrong TTL. I think the obvious way to address this is to stop using the "listening" socket to send datagrams for a flow, using a connect()ed socket instead. We have other reasons to do that too, and I'm working on implementing that right now. The question is whether this is a serious enough problem to delay this until the "both sides connect()ed sockets" change is merged.Now that ICMP pass-through from socket-to-tap is in place, it is easy to support UDP based traceroute functionality in direction tap-to-socket. We fix that in this commit. Link: https://bugs.passt.top/show_bug.cgi?id=64 Signed-off-by: Jon Maloy <jmaloy(a)redhat.com>Reviewed-by: David Gibson <david(a)gibson.dropbear.id.au> One commont below.I haven't reviewed the series yet, but I don't think that an eventual re-spin would change this, so... problem solved I guess? I can just wait and apply them together.Yeah, I guess so. Hooray! -- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson