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>

3 files changed, 15 insertions, 11 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 27b652f379ef..09cb5c11ceea 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1300,7 +1300,8 @@ void tcp_free_fastopen_req(struct tcp_sock *tp);
 
 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
-void tcp_fastopen_cookie_gen(__be32 addr, struct tcp_fastopen_cookie *foc);
+extern void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
+                                    struct tcp_fastopen_cookie *foc);
 
 #define TCP_FASTOPEN_KEY_LENGTH 16
 
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 8f7ef0ad80e5..ab7bd35bb312 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();
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 280efe5f19c1..ec2702882d8d 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1316,9 +1316,11 @@ static bool tcp_fastopen_check(struct sock *sk, struct sk_buff *skb,
                 tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
                 return true;
         }
+
         if (foc->len == TCP_FASTOPEN_COOKIE_SIZE) {
                 if ((sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_CHKED) == 0) {
-                        tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr, valid_foc);
+                        tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr,
+                                                ip_hdr(skb)->daddr, valid_foc);
                         if ((valid_foc->len != TCP_FASTOPEN_COOKIE_SIZE) ||
                             memcmp(&foc->val[0], &valid_foc->val[0],
                             TCP_FASTOPEN_COOKIE_SIZE) != 0)
@@ -1329,14 +1331,16 @@ static bool tcp_fastopen_check(struct sock *sk, struct sk_buff *skb,
                 tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
                 return true;
         } else if (foc->len == 0) { /* Client requesting a cookie */
-                tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr, valid_foc);
+                tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr,
+                                        ip_hdr(skb)->daddr, valid_foc);
                 NET_INC_STATS_BH(sock_net(sk),
                     LINUX_MIB_TCPFASTOPENCOOKIEREQD);
         } else {
                 /* Client sent a cookie with wrong size. Treat it
                  * the same as invalid and return a valid one.
                  */
-                tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr, valid_foc);
+                tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr,
+                                        ip_hdr(skb)->daddr, valid_foc);
         }
         return false;
 }