netdev - [RFC 2/2] udp: Support SO_DELAYED

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Date:   Wed, 31 Oct 2018 16:26:35 -0700
From:   Christoph Paasch <cpaasch@...le.com>
To:     netdev@...r.kernel.org
Cc:     Ian Swett <ianswett@...gle.com>,
        Leif Hedstrom <lhedstrom@...le.com>,
        Jana Iyengar <jri.ietf@...il.com>
Subject: [RFC 2/2] udp: Support SO_DELAYED_BIND

For UDP, there is only a single socket-hash table, the udptable.

We want to prevent incoming segments to match on this socket when
SO_DELAYED_BIND is set. Thus, when computing the score for unconnected
sockets, we simply prevent the match as long as the flag is set.

Signed-off-by: Christoph Paasch <cpaasch@...le.com>
---
 net/ipv4/datagram.c | 1 +
 net/ipv4/udp.c      | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/net/ipv4/datagram.c b/net/ipv4/datagram.c
index 300921417f89..9bf0e0d2ea33 100644
--- a/net/ipv4/datagram.c
+++ b/net/ipv4/datagram.c
@@ -78,6 +78,7 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
 	inet->inet_id = jiffies;
 
 	sk_dst_set(sk, &rt->dst);
+	sock_reset_flag(sk, SOCK_DELAYED_BIND);
 	err = 0;
 out:
 	return err;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index ca3ed931f2a9..fb55f925342b 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -408,6 +408,9 @@ static int compute_score(struct sock *sk, struct net *net,
 			score += 4;
 	}
 
+	if (sock_flag(sk, SOCK_DELAYED_BIND))
+		return -1;
+
 	if (sk->sk_incoming_cpu == raw_smp_processor_id())
 		score++;
 	return score;
-- 
2.16.2