Re: EINVAL when using connect() for udp sockets

[Eric Dumazet]

On Tue, 2017-03-28 at 16:11 -0700, Eric Dumazet wrote:

> Yes, this looks better.
> 
> Although you probably need to change a bit later this part :
> 
> if (!inet->inet_saddr)
>       inet->inet_saddr = fl4->saddr;  /* Update source address */
> 

I came up with the following tested patch for IPv4

diff --git a/net/ipv4/datagram.c b/net/ipv4/datagram.c
index 
f915abff1350a86af8d5bb89725b751c061b0fb5..1454b6191e0d38ffae0ae260578858285bc5f77b
 100644
--- a/net/ipv4/datagram.c
+++ b/net/ipv4/datagram.c
@@ -40,7 +40,7 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr 
*uaddr, int addr_len
        sk_dst_reset(sk);
 
        oif = sk->sk_bound_dev_if;
-       saddr = inet->inet_saddr;
+       saddr = (sk->sk_userlocks & SOCK_BINDADDR_LOCK) ? inet->inet_saddr : 0;
        if (ipv4_is_multicast(usin->sin_addr.s_addr)) {
                if (!oif)
                        oif = inet->mc_index;
@@ -64,9 +64,8 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr 
*uaddr, int addr_len
                err = -EACCES;
                goto out;
        }
-       if (!inet->inet_saddr)
+       if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK)) {
                inet->inet_saddr = fl4->saddr;  /* Update source address */
-       if (!inet->inet_rcv_saddr) {
                inet->inet_rcv_saddr = fl4->saddr;
                if (sk->sk_prot->rehash)
                        sk->sk_prot->rehash(sk);