ipv4: dccp: handle ICMP messages on DCCP_NEW_SYN_RECV request sockets

dccp_v4_err() can restrict lookups to ehash table, and not to listeners.

Note this patch creates the infrastructure, but this means that ICMP
messages for request sockets are ignored until complete conversion.

New dccp_req_err() helper is exported so that we can use it in IPv6
in following patch.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/dccp.h

@@ -43,6 +43,7 @@ enum dccp_state {
 	DCCP_CLOSING	     = TCP_CLOSING,
 	DCCP_TIME_WAIT	     = TCP_TIME_WAIT,
 	DCCP_CLOSED	     = TCP_CLOSE,
+	DCCP_NEW_SYN_RECV    = TCP_NEW_SYN_RECV,
 	DCCP_PARTOPEN	     = TCP_MAX_STATES,
 	DCCP_PASSIVE_CLOSEREQ,			/* clients receiving CloseReq */
 	DCCP_MAX_STATES
@@ -57,6 +58,7 @@ enum {
 	DCCPF_CLOSING	      = TCPF_CLOSING,
 	DCCPF_TIME_WAIT	      = TCPF_TIME_WAIT,
 	DCCPF_CLOSED	      = TCPF_CLOSE,
+	DCCPF_NEW_SYN_RECV    = TCPF_NEW_SYN_RECV,
 	DCCPF_PARTOPEN	      = (1 << DCCP_PARTOPEN),
 };
 

net/dccp/dccp.h

@@ -317,6 +317,7 @@ int inet_dccp_listen(struct socket *sock, int backlog);
 unsigned int dccp_poll(struct file *file, struct socket *sock,
 		       poll_table *wait);
 int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
+void dccp_req_err(struct sock *sk, u64 seq);
 
 struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *skb);
 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code);

net/dccp/ipv4.c

@@ -195,6 +195,32 @@ static void dccp_do_redirect(struct sk_buff *skb, struct sock *sk)
 		dst->ops->redirect(dst, sk, skb);
 }
 
+void dccp_req_err(struct sock *sk, u64 seq)
+	{
+	struct request_sock *req = inet_reqsk(sk);
+	struct net *net = sock_net(sk);
+
+	/*
+	 * ICMPs are not backlogged, hence we cannot get an established
+	 * socket here.
+	 */
+	WARN_ON(req->sk);
+
+	if (!between48(seq, dccp_rsk(req)->dreq_iss, dccp_rsk(req)->dreq_gss)) {
+		NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
+	} else {
+		/*
+		 * Still in RESPOND, just remove it silently.
+		 * There is no good way to pass the error to the newly
+		 * created socket, and POSIX does not want network
+		 * errors returned from accept().
+		 */
+		inet_csk_reqsk_queue_drop(req->rsk_listener, req);
+	}
+	reqsk_put(req);
+}
+EXPORT_SYMBOL(dccp_req_err);
+
 /*
  * This routine is called by the ICMP module when it gets some sort of error
  * condition. If err < 0 then the socket should be closed and the error
@@ -227,10 +253,11 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info)
 		return;
 	}
 
-	sk = inet_lookup(net, &dccp_hashinfo,
-			iph->daddr, dh->dccph_dport,
-			iph->saddr, dh->dccph_sport, inet_iif(skb));
-	if (sk == NULL) {
+	sk = __inet_lookup_established(net, &dccp_hashinfo,
+				       iph->daddr, dh->dccph_dport,
+				       iph->saddr, ntohs(dh->dccph_sport),
+				       inet_iif(skb));
+	if (!sk) {
 		ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
 		return;
 	}
@@ -239,6 +266,9 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info)
 		inet_twsk_put(inet_twsk(sk));
 		return;
 	}
+	seq = dccp_hdr_seq(dh);
+	if (sk->sk_state == DCCP_NEW_SYN_RECV)
+		return dccp_req_err(sk, seq);
 
 	bh_lock_sock(sk);
 	/* If too many ICMPs get dropped on busy
@@ -251,7 +281,6 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info)
 		goto out;
 
 	dp = dccp_sk(sk);
-	seq = dccp_hdr_seq(dh);
 	if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
 	    !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
 		NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
@@ -288,37 +317,6 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info)
 	}
 
 	switch (sk->sk_state) {
-		struct request_sock *req;
-	case DCCP_LISTEN:
-		if (sock_owned_by_user(sk))
-			goto out;
-		req = inet_csk_search_req(sk, dh->dccph_dport,
-					  iph->daddr, iph->saddr);
-		if (!req)
-			goto out;
-
-		/*
-		 * ICMPs are not backlogged, hence we cannot get an established
-		 * socket here.
-		 */
-		WARN_ON(req->sk);
-
-		if (!between48(seq, dccp_rsk(req)->dreq_iss,
-				    dccp_rsk(req)->dreq_gss)) {
-			NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
-			reqsk_put(req);
-			goto out;
-		}
-		/*
-		 * Still in RESPOND, just remove it silently.
-		 * There is no good way to pass the error to the newly
-		 * created socket, and POSIX does not want network
-		 * errors returned from accept().
-		 */
-		inet_csk_reqsk_queue_drop(sk, req);
-		reqsk_put(req);
-		goto out;
-
 	case DCCP_REQUESTING:
 	case DCCP_RESPOND:
 		if (!sock_owned_by_user(sk)) {