tcp: add server ip to encrypt cookie in fast open

Encrypt the cookie with both server and client IPv4 addresses,
such that multi-homed server will grant different cookies
based on both the source and destination IPs. No client change
is needed since cookie is opaque to the client.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 7 deletions

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 8f7ef0a..ab7bd35 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -58,23 +58,22 @@ error:		kfree(ctx);
 	return err;
 }
 
-/* Computes the fastopen cookie for the peer.
- * The peer address is a 128 bits long (pad with zeros for IPv4).
+/* Computes the fastopen cookie for the IP path.
+ * The path is a 128 bits long (pad with zeros for IPv4).
  *
  * The caller must check foc->len to determine if a valid cookie
  * has been generated successfully.
 */
-void tcp_fastopen_cookie_gen(__be32 addr, struct tcp_fastopen_cookie *foc)
+void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
+			     struct tcp_fastopen_cookie *foc)
 {
-	__be32 peer_addr[4] = { addr, 0, 0, 0 };
+	__be32 path[4] = { src, dst, 0, 0 };
 	struct tcp_fastopen_context *ctx;
 
 	rcu_read_lock();
 	ctx = rcu_dereference(tcp_fastopen_ctx);
 	if (ctx) {
-		crypto_cipher_encrypt_one(ctx->tfm,
-					  foc->val,
-					  (__u8 *)peer_addr);
+		crypto_cipher_encrypt_one(ctx->tfm, foc->val, (__u8 *)path);
 		foc->len = TCP_FASTOPEN_COOKIE_SIZE;
 	}
 	rcu_read_unlock();