On Mon, Dec 15, 2025 at 03:11:22PM +0100, Stefano Garzarella wrote: > On Fri, Dec 12, 2025 at 07:26:15AM -0800, Bobby Eshleman wrote: > > On Tue, Dec 02, 2025 at 02:01:04PM -0800, Bobby Eshleman wrote: > > > On Tue, Dec 02, 2025 at 09:47:19PM +0100, Paolo Abeni wrote: > > > > On 12/2/25 6:56 PM, Bobby Eshleman wrote: > > > > > On Tue, Dec 02, 2025 at 11:18:14AM +0100, Paolo Abeni wrote: > > > > >> On 11/27/25 8:47 AM, Bobby Eshleman wrote: > > > > >>> @@ -674,6 +689,17 @@ static int vhost_vsock_dev_open(struct inode > > > > >>> *inode, struct file *file) > > > > >>> goto out; > > > > >>> } > > > > >>> > > > > >>> + net = current->nsproxy->net_ns; > > > > >>> + vsock->net = get_net_track(net, &vsock->ns_tracker, GFP_KERNEL); > > > > >>> + > > > > >>> + /* Store the mode of the namespace at the time of creation. If > > > > >>> this > > > > >>> + * namespace later changes from "global" to "local", we want > > > > >>> this vsock > > > > >>> + * to continue operating normally and not suddenly break. For > > > > >>> that > > > > >>> + * reason, we save the mode here and later use it when > > > > >>> performing > > > > >>> + * socket lookups with vsock_net_check_mode() (see > > > > >>> vhost_vsock_get()). > > > > >>> + */ > > > > >>> + vsock->net_mode = vsock_net_mode(net); > > > > >> > > > > >> I'm sorry for the very late feedback. I think that at very least the > > > > >> user-space needs a way to query if the given transport is in local or > > > > >> global mode, as AFAICS there is no way to tell that when socket > > > > >> creation > > > > >> races with mode change. > > > > > > > > > > Are you thinking something along the lines of sockopt? > > > > > > > > I'd like to see a way for the user-space to query the socket 'namespace > > > > mode'. > > > > > > > > sockopt could be an option; a possibly better one could be sock_diag. Or > > > > you could do both using dumping the info with a shared helper invoked by > > > > both code paths, alike what TCP is doing. > > > > >> Also I'm a bit uneasy with the model implemented here, as 'local' > > > > >> socket > > > > >> may cross netns boundaris and connect to 'local' socket in other > > > > >> netns > > > > >> (if I read correctly patch 2/12). That in turns AFAICS break the > > > > >> netns > > > > >> isolation. > > > > > > > > > > Local mode sockets are unable to communicate with local mode (and > > > > > global > > > > > mode too) sockets that are in other namespaces. The key piece of code > > > > > for that is vsock_net_check_mode(), where if either modes is local the > > > > > namespaces must be the same. > > > > > > > > Sorry, I likely misread the large comment in patch 2: > > > > > > > > https://lore.kernel.org/netdev/[email protected]/ > > > > > > > > >> Have you considered instead a slightly different model, where the > > > > >> local/global model is set in stone at netns creation time - alike > > > > >> what > > > > >> /proc/sys/net/ipv4/tcp_child_ehash_entries is doing[1] - and > > > > >> inter-netns connectivity is explicitly granted by the admin (I guess > > > > >> you will need new transport operations for that)? > > > > >> > > > > >> /P > > > > >> > > > > >> [1] tcp allows using per-netns established socket lookup tables - as > > > > >> opposed to the default global lookup table (even if match always > > > > >> takes > > > > >> in account the netns obviously). The mentioned sysctl specify such > > > > >> configuration for the children namespaces, if any. > > > > > > > > > > I'll save this discussion if the above doesn't resolve your concerns. > > > > I still have some concern WRT the dynamic mode change after netns > > > > creation. I fear some 'unsolvable' (or very hard to solve) race I can't > > > > see now. A tcp_child_ehash_entries-like model will avoid completely the > > > > issue, but I understand it would be a significant change over the > > > > current status. > > > > > > > > "Luckily" the merge window is on us and we have some time to discuss. Do > > > > you have a specific use-case for the ability to change the netns > > > > mode > > > > after creation? > > > > > > > > /P > > > > > > I don't think there is a hard requirement that the mode be change-able > > > after creation. Though I'd love to avoid such a big change... or at > > > least leave unchanged as much of what we've already reviewed as > > > possible. > > > > > > In the scheme of defining the mode at creation and following the > > > tcp_child_ehash_entries-ish model, what I'm imagining is: > > > - /proc/sys/net/vsock/child_ns_mode can be set to "local" or "global" > > > - /proc/sys/net/vsock/child_ns_mode is not immutable, can change any > > > number of times > > > > > > - when a netns is created, the new netns mode is inherited from > > > child_ns_mode, being assigned using something like: > > > > > > net->vsock.ns_mode = > > > get_net_ns_by_pid(current->pid)->child_ns_mode > > > > > > - /proc/sys/net/vsock/ns_mode queries the current mode, returning > > > "local" or "global", returning value of net->vsock.ns_mode > > > - /proc/sys/net/vsock/ns_mode and net->vsock.ns_mode are immutable and > > > reject writes > > > > > > Does that align with what you have in mind? > > > > Hey Paolo, I just wanted to sync up on this one. Does the above align > > with what you envision? > > Hi Bobby, AFAIK Paolo was at LPC, so there could be some delay. > > FYI I'll be off from Dec 25 to Jan 6, so if we want to do an RFC in the > middle, I'll do my best to take a look before my time off. > > Thanks, > Stefano >
Sounds like a plan, thanks! Best, Bobby
