Re: [PATCH v3 08/10] libmpathcmd: try both abstract and pathname sockets

[Benjamin Marzinski <bmarzins@redhat.com>]

On Fri, Feb 14, 2025 at 11:10:09PM +0100, Martin Wilck wrote:
> When connecting to the multipathd socket, try the pathname socket
> first, then the abstract socket. Fail only if both connection attempts
> fail.
> 
> Signed-off-by: Martin Wilck <mwilck@suse.com>
> ---
>  libmpathcmd/mpath_cmd.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/libmpathcmd/mpath_cmd.c b/libmpathcmd/mpath_cmd.c
> index c7cf954..ba5bb31 100644
> --- a/libmpathcmd/mpath_cmd.c
> +++ b/libmpathcmd/mpath_cmd.c
> @@ -102,7 +102,10 @@ int mpath_connect__(int nonblocking)
>  	size_t len;
>  	struct sockaddr_un addr;
>  	int flags = 0;
> +	const char *names[2] = {PATHNAME_SOCKET, ABSTRACT_SOCKET};
> +	int name_idx = 0;
>  
> +retry:
>  	fd = socket(AF_LOCAL, SOCK_STREAM, 0);
>  	if (fd == -1)
>  		return -1;
> @@ -113,13 +116,17 @@ int mpath_connect__(int nonblocking)
>  			(void)fcntl(fd, F_SETFL, flags|O_NONBLOCK);
>  	}
>  
> -	len = mpath_fill_sockaddr__(&addr, ABSTRACT_SOCKET);
> +	len = mpath_fill_sockaddr__(&addr, names[name_idx]);
>  	if (connect(fd, (struct sockaddr *)&addr, len) == -1) {
>  		int err = errno;
>  
>  		close(fd);
> -		errno = err;
> -		return -1;
> +		if (err == ECONNREFUSED && ++name_idx == 1)

Most of the connect() return codes are things that could presumably be
fixed by trying a different address (not the errors related to a problem
with sockfd, but we just created the socket, so those seem pretty
impossible). Is there a reason why we don't just retry on any error?

-Ben

> +			goto retry;
> +		else {
> +			errno = err;
> +			return -1;
> +		}
>  	}
>  
>  	if (nonblocking && flags != -1)
> -- 
> 2.48.1