Re: [PATCH v2 3/3] tcp: Simplify handling of getsockname()

[Stefano Brivio <sbrivio@redhat.com>]

On Tue,  4 Feb 2025 16:42:15 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> For migration we need to get the specific local address and port for
> connected sockets with getsockname().  We currently open code marshalling
> the results into the flow entry.
> 
> However, we already have inany_from_sockaddr() which handles the fiddly
> parts of this, so use it.  Also report failures, which may make debugging
> problems easier.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  tcp.c | 24 +++++++-----------------
>  1 file changed, 7 insertions(+), 17 deletions(-)
> 
> diff --git a/tcp.c b/tcp.c
> index 7ce0f4cb..dbdaa9d9 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -1712,24 +1712,14 @@ static void tcp_conn_from_tap(const struct ctx *c, sa_family_t af,
>  	tcp_epoll_ctl(c, conn);
>  
>  	if (c->mode == MODE_VU) { /* To rebind to same oport after migration */
> -		if (af == AF_INET) {
> -			struct sockaddr_in s_in;
> -
> -			sl = sizeof(s_in);
> -			if (!getsockname(s, (struct sockaddr *)&s_in, &sl)) {
> -				/* NOLINTNEXTLINE(clang-analyzer-core.CallAndMessage) */
> -				tgt->oport = ntohs(s_in.sin_port);
> -				tgt->oaddr = inany_from_v4(s_in.sin_addr);
> -			}
> -		} else {
> -			struct sockaddr_in6 s_in6;
> +		union sockaddr_inany sa;
> +		socklen_t sl = sizeof(sa);

This shadows the previous declaration of 'sl'. Turning into an
assignment.

> -			sl = sizeof(s_in6);
> -			if (!getsockname(s, (struct sockaddr *)&s_in6, &sl)) {
> -				/* NOLINTNEXTLINE(clang-analyzer-core.CallAndMessage) */
> -				tgt->oport = ntohs(s_in6.sin6_port);
> -				tgt->oaddr.a6 = s_in6.sin6_addr;
> -			}
> +		if (!getsockname(s, &sa.sa, &sl)) {
> +			inany_from_sockaddr(&tgt->oaddr, &tgt->oport, &sa);
> +		} else {
> +			err("Failed to get local address for socket: %s",
> +			    strerror_(errno));
>  		}
>  	}

-- 
Stefano