On Wed, Feb 3, 2021 at 5:14 PM David Howells <dhowe...@redhat.com> wrote:
>
> Xin Long <lucien....@gmail.com> wrote:
>
> > BTW, I'm also thinking to use udp_sock_create(), the only problem I can
> > see is it may not do bind() in rxrpc_open_socket(), is that true? or we
> > can actually bind to some address when a local address is not supplied?
>
> If a local address isn't explicitly bound to the AF_RXRPC socket, binding the
> UDP socket to a random local port is fine. In fact, sometimes I want to
> explicitly bind an rxrpc server socket to a random port. See fs/afs/rxrpc.c
> function afs_open_socket():
>
> /* bind the callback manager's address to make this a server socket */
> memset(&srx, 0, sizeof(srx));
> srx.srx_family = AF_RXRPC;
> srx.srx_service = CM_SERVICE;
> srx.transport_type = SOCK_DGRAM;
> srx.transport_len = sizeof(srx.transport.sin6);
> srx.transport.sin6.sin6_family = AF_INET6;
> srx.transport.sin6.sin6_port = htons(AFS_CM_PORT);
> ...
> ret = kernel_bind(socket, (struct sockaddr *) &srx, sizeof(srx));
> if (ret == -EADDRINUSE) {
> srx.transport.sin6.sin6_port = 0;
>
> ^^^ That's hoping to get a random port bound.
>
> ret = kernel_bind(socket, (struct sockaddr *) &srx,
> sizeof(srx));
> }
> if (ret < 0)
> goto error_2;
>
> The client cache manager server socket here is used to receive notifications
> back from the fileserver. There's a standard port (7001) for the service, but
> if that's in use, we can use any other port. The fileserver grabs the source
> port from incoming RPC requests - and then uses that when sending 3rd-party
> change notifications back.
>
> If you could arrange for a random port to be assigned in such a case (and
> indicated back to the caller), that would be awesome. Possibly I just don't
> need to actually use bind in this case.
>
The patch is attached (based on this patch):
+ udp_conf.family = srx->transport.family;
+ if (udp_conf.family == AF_INET) {
+ udp_conf.local_ip = srx->transport.sin.sin_addr;
+ udp_conf.local_udp_port = srx->transport.sin.sin_port;
+ } else {
+ udp_conf.local_ip6 = srx->transport.sin6.sin6_addr;
+ udp_conf.local_udp_port = srx->transport.sin6.sin6_port;
+ }
+ ret = udp_sock_create(net, &udp_conf, &local->socket);
I think this will work well. When the socket is not bound,
srx->transport.sin.sin(6)_addr/sin(6)_port are zero. It'll
bind to a random port in udp_sock_create().
BTW: do you have any testing for this?
Thanks.
0001-rxrpc-use-udp-tunnel-APIs-instead-of-open-code-in-rx.patch
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