[PATCH] SUNRPC: prevent port reuse on transports which don't request it.

[PATCH] SUNRPC: prevent port reuse on transports which don't request it.

[NeilBrown]

If an RPC client is created without RPC_CLNT_CREATE_REUSEPORT, it should
not reuse the source port when a TCP connection is re-established.
This is currently implemented by preventing the source port being
recorded after a successful connection (the call to xs_set_srcport()).

However the source port is also recorded after a successful bind in xs_bind().
This may not be needed at all and certainly is not wanted when
RPC_CLNT_CREATE_REUSEPORT wasn't requested.

So avoid that assignment when xprt.reuseport is not set.

With this change, NFSv4.1 and later mounts use a different port number on
each connection.  This is helpful with some firewalls which don't cope
well with port reuse.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 net/sunrpc/xprtsock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 316d04945587..3228b7a1836a 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1689,7 +1689,8 @@ static int xs_bind(struct sock_xprt *transport, struct socket *sock)
 		err = kernel_bind(sock, (struct sockaddr *)&myaddr,
 				transport->xprt.addrlen);
 		if (err == 0) {
-			transport->srcport = port;
+			if (transport->xprt.reuseport)
+				transport->srcport = port;
 			break;
 		}
 		last = port;
-- 
2.31.1

Re: [PATCH] SUNRPC: prevent port reuse on transports which don't request it.

[NeilBrown]

On Tue, 15 Jun 2021, someone wrote:
> If an RPC client is created without RPC_CLNT_CREATE_REUSEPORT, it should
> not reuse the source port when a TCP connection is re-established.
> This is currently implemented by preventing the source port being
> recorded after a successful connection (the call to xs_set_srcport()).
> 
> However the source port is also recorded after a successful bind in xs_bind().
> This may not be needed at all and certainly is not wanted when
> RPC_CLNT_CREATE_REUSEPORT wasn't requested.
> 
> So avoid that assignment when xprt.reuseport is not set.
> 
> With this change, NFSv4.1 and later mounts use a different port number on
> each connection.  This is helpful with some firewalls which don't cope
> well with port reuse.
> 
> Signed-off-by: NeilBrown <neilb@suse.de>

I guess this should have

Fixes: e6237b6feb37 ("NFSv4.1: Don't rebind to the same source port when reconnecting to the server")

NeilBrown

> ---
>  net/sunrpc/xprtsock.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index 316d04945587..3228b7a1836a 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -1689,7 +1689,8 @@ static int xs_bind(struct sock_xprt *transport, struct socket *sock)
>  		err = kernel_bind(sock, (struct sockaddr *)&myaddr,
>  				transport->xprt.addrlen);
>  		if (err == 0) {
> -			transport->srcport = port;
> +			if (transport->xprt.reuseport)
> +				transport->srcport = port;
>  			break;
>  		}
>  		last = port;
> -- 
> 2.31.1
> 
>