netdev - Re: [PATCH v1 net] net: Return errno in sk->sk_prot->get

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Date:   Fri, 18 Nov 2022 10:35:07 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Kuniyuki Iwashima <kuniyu@...zon.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        David Ahern <dsahern@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Cc:     Christoph Paasch <cpaasch@...le.com>,
        Florian Westphal <fw@...len.de>,
        Peter Krystad <peter.krystad@...ux.intel.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org,
        mptcp@...ts.linux.dev
Subject: Re: [PATCH v1 net] net: Return errno in sk->sk_prot->get_port().

On Thu, 2022-11-17 at 10:47 -0800, Kuniyuki Iwashima wrote:
> We assume the correct errno is -EADDRINUSE when sk->sk_prot->get_port()
> fails, so some ->get_port() functions return just 1 on failure and the
> callers return -EADDRINUSE instead.
> 
> However, mptcp_get_port() can return -EINVAL.  Let's not ignore the error.

Note that such return value is on a WARN_ON_ONCE() check. I think such
condition is actually an overzealot error checking and we could
possibly/likelly remove it in the future.

Still the change below IMHO makes the code cleaner, so I'm not
opposing. Possibly could be targeting net-next instead.

Thanks,

Paolo

> Note the only exception is inet_autobind(), all of whose callers return
> -EAGAIN instead.
> 
> Fixes: cec37a6e41aa ("mptcp: Handle MP_CAPABLE options for outgoing connections")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---
>  net/ipv4/af_inet.c              | 4 ++--
>  net/ipv4/inet_connection_sock.c | 7 ++++---
>  net/ipv4/ping.c                 | 2 +-
>  net/ipv4/udp.c                  | 2 +-
>  net/ipv6/af_inet6.c             | 4 ++--
>  5 files changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index 4728087c42a5..4799eb55c830 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -522,9 +522,9 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
>  	/* Make sure we are allowed to bind here. */
>  	if (snum || !(inet->bind_address_no_port ||
>  		      (flags & BIND_FORCE_ADDRESS_NO_PORT))) {
> -		if (sk->sk_prot->get_port(sk, snum)) {
> +		err = sk->sk_prot->get_port(sk, snum);
> +		if (err) {
>  			inet->inet_saddr = inet->inet_rcv_saddr = 0;
> -			err = -EADDRINUSE;
>  			goto out_release_sock;
>  		}
>  		if (!(flags & BIND_FROM_BPF)) {
> diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
> index 4e84ed21d16f..4a34bc7cb15e 100644
> --- a/net/ipv4/inet_connection_sock.c
> +++ b/net/ipv4/inet_connection_sock.c
> @@ -471,11 +471,11 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
>  	bool reuse = sk->sk_reuse && sk->sk_state != TCP_LISTEN;
>  	bool found_port = false, check_bind_conflict = true;
>  	bool bhash_created = false, bhash2_created = false;
> +	int ret = -EADDRINUSE, port = snum, l3mdev;
>  	struct inet_bind_hashbucket *head, *head2;
>  	struct inet_bind2_bucket *tb2 = NULL;
>  	struct inet_bind_bucket *tb = NULL;
>  	bool head2_lock_acquired = false;
> -	int ret = 1, port = snum, l3mdev;
>  	struct net *net = sock_net(sk);
>  
>  	l3mdev = inet_sk_bound_l3mdev(sk);
> @@ -1186,7 +1186,7 @@ int inet_csk_listen_start(struct sock *sk)
>  {
>  	struct inet_connection_sock *icsk = inet_csk(sk);
>  	struct inet_sock *inet = inet_sk(sk);
> -	int err = -EADDRINUSE;
> +	int err;
>  
>  	reqsk_queue_alloc(&icsk->icsk_accept_queue);
>  
> @@ -1202,7 +1202,8 @@ int inet_csk_listen_start(struct sock *sk)
>  	 * after validation is complete.
>  	 */
>  	inet_sk_state_store(sk, TCP_LISTEN);
> -	if (!sk->sk_prot->get_port(sk, inet->inet_num)) {
> +	err = sk->sk_prot->get_port(sk, inet->inet_num);
> +	if (!err) {
>  		inet->inet_sport = htons(inet->inet_num);
>  
>  		sk_dst_reset(sk);
> diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
> index bde333b24837..bb9854c2b7a1 100644
> --- a/net/ipv4/ping.c
> +++ b/net/ipv4/ping.c
> @@ -138,7 +138,7 @@ int ping_get_port(struct sock *sk, unsigned short ident)
>  
>  fail:
>  	spin_unlock(&ping_table.lock);
> -	return 1;
> +	return -EADDRINUSE;
>  }
>  EXPORT_SYMBOL_GPL(ping_get_port);
>  
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 6a320a614e54..b30137f48fff 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -234,7 +234,7 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
>  {
>  	struct udp_hslot *hslot, *hslot2;
>  	struct udp_table *udptable = sk->sk_prot->h.udp_table;
> -	int    error = 1;
> +	int error = -EADDRINUSE;
>  	struct net *net = sock_net(sk);
>  
>  	if (!snum) {
> diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
> index 024191004982..7b0cd54da452 100644
> --- a/net/ipv6/af_inet6.c
> +++ b/net/ipv6/af_inet6.c
> @@ -409,10 +409,10 @@ static int __inet6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
>  	/* Make sure we are allowed to bind here. */
>  	if (snum || !(inet->bind_address_no_port ||
>  		      (flags & BIND_FORCE_ADDRESS_NO_PORT))) {
> -		if (sk->sk_prot->get_port(sk, snum)) {
> +		err = sk->sk_prot->get_port(sk, snum);
> +		if (err) {
>  			sk->sk_ipv6only = saved_ipv6only;
>  			inet_reset_saddr(sk);
> -			err = -EADDRINUSE;
>  			goto out;
>  		}
>  		if (!(flags & BIND_FROM_BPF)) {

Th