[PATCH 10/19] tcp: ipv6: Add AO signing for tcp_v6_send_response

[Leonard Crestez <cdleonard@xxxxxxxxx>]

This is a special code path for acks and resets outside of normal
connection establishment and closing.

Signed-off-by: Leonard Crestez <cdleonard@xxxxxxxxx>
---
 net/ipv6/tcp_ipv6.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 724145ddf122..d922219af20e 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -896,13 +896,37 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
 	struct sock *ctl_sk = net->ipv6.tcp_sk;
 	unsigned int tot_len = sizeof(struct tcphdr);
 	__be32 mrst = 0, *topt;
 	struct dst_entry *dst;
 	__u32 mark = 0;
+#ifdef CONFIG_TCP_AUTHOPT
+	struct tcp_authopt_info *authopt_info = NULL;
+	struct tcp_authopt_key_info *authopt_key_info = NULL;
+	u8 authopt_rnextkeyid;
+#endif
 
 	if (tsecr)
 		tot_len += TCPOLEN_TSTAMP_ALIGNED;
+#ifdef CONFIG_TCP_AUTHOPT
+	/* Key lookup before SKB allocation */
+	if (static_branch_unlikely(&tcp_authopt_needed) && sk)
+	{
+		if (sk->sk_state == TCP_TIME_WAIT)
+			authopt_info = tcp_twsk(sk)->tw_authopt_info;
+		else
+			authopt_info = rcu_dereference(tcp_sk(sk)->authopt_info);
+
+		if (authopt_info) {
+			authopt_key_info = __tcp_authopt_select_key(sk, authopt_info, sk, &authopt_rnextkeyid);
+			if (authopt_key_info) {
+				tot_len += TCPOLEN_AUTHOPT_OUTPUT;
+				/* Don't use MD5 */
+				key = NULL;
+			}
+		}
+	}
+#endif
 #ifdef CONFIG_TCP_MD5SIG
 	if (key)
 		tot_len += TCPOLEN_MD5SIG_ALIGNED;
 #endif
 
@@ -955,10 +979,21 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
 		tcp_v6_md5_hash_hdr((__u8 *)topt, key,
 				    &ipv6_hdr(skb)->saddr,
 				    &ipv6_hdr(skb)->daddr, t1);
 	}
 #endif
+#ifdef CONFIG_TCP_AUTHOPT
+	/* Compute the TCP-AO mac. Unlike in the ipv4 case we have a real SKB */
+	if (static_branch_unlikely(&tcp_authopt_needed) && authopt_key_info)
+	{
+		*topt++ = htonl((TCPOPT_AUTHOPT << 24) |
+				(TCPOLEN_AUTHOPT_OUTPUT << 16) |
+				(authopt_key_info->send_id << 8) |
+				(authopt_rnextkeyid));
+		tcp_authopt_hash((char*)topt, authopt_key_info, (struct sock*)sk, buff);
+	}
+#endif
 
 	memset(&fl6, 0, sizeof(fl6));
 	fl6.daddr = ipv6_hdr(skb)->saddr;
 	fl6.saddr = ipv6_hdr(skb)->daddr;
 	fl6.flowlabel = label;
-- 
2.25.1