Re: [PATCH RFC net 1/2] datagram: Rehash sockets only if local address changed for their family

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Stefano Brivio wrote:
> It makes no sense to rehash an IPv4 socket when we change
> sk_v6_rcv_saddr, or to rehash an IPv6 socket as inet_rcv_saddr is set:
> the secondary hash (including the local address) won't change, because
> ipv4_portaddr_hash() and ipv6_portaddr_hash() only take the address
> matching the socket family.

Even if this is correct, it sounds like an optimization.
If so, it belongs in net-next.

Avoid making a fix (to net and eventually stable kernels) conditional
on optimizations that are not suitable for stable cherry-picks.

> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> ---
>  net/ipv4/datagram.c | 2 +-
>  net/ipv6/datagram.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/datagram.c b/net/ipv4/datagram.c
> index cc6d0bd7b0a9..d52333e921f3 100644
> --- a/net/ipv4/datagram.c
> +++ b/net/ipv4/datagram.c
> @@ -65,7 +65,7 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
>  		inet->inet_saddr = fl4->saddr;	/* Update source address */
>  	if (!inet->inet_rcv_saddr) {
>  		inet->inet_rcv_saddr = fl4->saddr;
> -		if (sk->sk_prot->rehash)
> +		if (sk->sk_prot->rehash && sk->sk_family == AF_INET)
>  			sk->sk_prot->rehash(sk);

When is sk_family != AF_INET in __ip4_datagram_connect?


>  	}
>  	inet->inet_daddr = fl4->daddr;
> diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
> index fff78496803d..5c28a11128c7 100644
> --- a/net/ipv6/datagram.c
> +++ b/net/ipv6/datagram.c
> @@ -211,7 +211,7 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
>  		    ipv6_mapped_addr_any(&sk->sk_v6_rcv_saddr)) {
>  			ipv6_addr_set_v4mapped(inet->inet_rcv_saddr,
>  					       &sk->sk_v6_rcv_saddr);
> -			if (sk->sk_prot->rehash)
> +			if (sk->sk_prot->rehash && sk->sk_family == AF_INET6)
>  				sk->sk_prot->rehash(sk);

Even if this is a v4mappedv6 address, sk_family will be AF_INET6.