udp: remove headers from UDP packets before queueing

Remove UDP transport headers before queueing packets for reception.
This change simplifies a follow-up patch to add MSG_PEEK support.
Signed-off-by: NSam Kumar <samanthakumar@google.com>
Signed-off-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -1864,6 +1864,7 @@ void sk_reset_timer(struct sock *sk, struct timer_list *timer,
 
 void sk_stop_timer(struct sock *sk, struct timer_list *timer);
 
+int __sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
 int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
 
 int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb);

include/net/udp.h

@@ -158,6 +158,15 @@ static inline __sum16 udp_v4_check(int len, __be32 saddr,
 void udp_set_csum(bool nocheck, struct sk_buff *skb,
 		  __be32 saddr, __be32 daddr, int len);
 
+static inline void udp_csum_pull_header(struct sk_buff *skb)
+{
+	if (skb->ip_summed == CHECKSUM_NONE)
+		skb->csum = csum_partial(udp_hdr(skb), sizeof(struct udphdr),
+					 skb->csum);
+	skb_pull_rcsum(skb, sizeof(struct udphdr));
+	UDP_SKB_CB(skb)->cscov -= sizeof(struct udphdr);
+}
+
 struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
 				 struct udphdr *uh);
 int udp_gro_complete(struct sk_buff *skb, int nhoff);

net/core/sock.c

@@ -402,9 +402,8 @@ static void sock_disable_timestamp(struct sock *sk, unsigned long flags)
 }
 
 
-int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
+int __sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
-	int err;
 	unsigned long flags;
 	struct sk_buff_head *list = &sk->sk_receive_queue;
 
@@ -414,10 +413,6 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		return -ENOMEM;
 	}
 
-	err = sk_filter(sk, skb);
-	if (err)
-		return err;
-
 	if (!sk_rmem_schedule(sk, skb, skb->truesize)) {
 		atomic_inc(&sk->sk_drops);
 		return -ENOBUFS;
@@ -440,6 +435,18 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		sk->sk_data_ready(sk);
 	return 0;
 }
+EXPORT_SYMBOL(__sock_queue_rcv_skb);
+
+int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
+{
+	int err;
+
+	err = sk_filter(sk, skb);
+	if (err)
+		return err;
+
+	return __sock_queue_rcv_skb(sk, skb);
+}
 EXPORT_SYMBOL(sock_queue_rcv_skb);
 
 int sk_receive_skb(struct sock *sk, struct sk_buff *skb, const int nested)

net/ipv4/udp.c

@@ -1309,7 +1309,7 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 	if (!skb)
 		goto out;
 
-	ulen = skb->len - sizeof(struct udphdr);
+	ulen = skb->len;
 	copied = len;
 	if (copied > ulen)
 		copied = ulen;
@@ -1329,11 +1329,9 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 	}
 
 	if (checksum_valid || skb_csum_unnecessary(skb))
-		err = skb_copy_datagram_msg(skb, sizeof(struct udphdr),
-					    msg, copied);
+		err = skb_copy_datagram_msg(skb, 0, msg, copied);
 	else {
-		err = skb_copy_and_csum_datagram_msg(skb, sizeof(struct udphdr),
-						     msg);
+		err = skb_copy_and_csum_datagram_msg(skb, 0, msg);
 
 		if (err == -EINVAL)
 			goto csum_copy_err;
@@ -1500,7 +1498,7 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		sk_incoming_cpu_update(sk);
 	}
 
-	rc = sock_queue_rcv_skb(sk, skb);
+	rc = __sock_queue_rcv_skb(sk, skb);
 	if (rc < 0) {
 		int is_udplite = IS_UDPLITE(sk);
 
@@ -1616,10 +1614,14 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		}
 	}
 
-	if (rcu_access_pointer(sk->sk_filter) &&
-	    udp_lib_checksum_complete(skb))
+	if (rcu_access_pointer(sk->sk_filter)) {
+		if (udp_lib_checksum_complete(skb))
 			goto csum_error;
+		if (sk_filter(sk, skb))
+			goto drop;
+	}
 
+	udp_csum_pull_header(skb);
 	if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {
 		UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_RCVBUFERRORS,
 				 is_udplite);

net/ipv6/udp.c

@@ -376,7 +376,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 	if (!skb)
 		goto out;
 
-	ulen = skb->len - sizeof(struct udphdr);
+	ulen = skb->len;
 	copied = len;
 	if (copied > ulen)
 		copied = ulen;
@@ -398,10 +398,9 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 	}
 
 	if (checksum_valid || skb_csum_unnecessary(skb))
-		err = skb_copy_datagram_msg(skb, sizeof(struct udphdr),
-					    msg, copied);
+		err = skb_copy_datagram_msg(skb, 0, msg, copied);
 	else {
-		err = skb_copy_and_csum_datagram_msg(skb, sizeof(struct udphdr), msg);
+		err = skb_copy_and_csum_datagram_msg(skb, 0, msg);
 		if (err == -EINVAL)
 			goto csum_copy_err;
 	}
@@ -554,7 +553,7 @@ static int __udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		sk_incoming_cpu_update(sk);
 	}
 
-	rc = sock_queue_rcv_skb(sk, skb);
+	rc = __sock_queue_rcv_skb(sk, skb);
 	if (rc < 0) {
 		int is_udplite = IS_UDPLITE(sk);
 
@@ -648,8 +647,11 @@ int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	if (rcu_access_pointer(sk->sk_filter)) {
 		if (udp_lib_checksum_complete(skb))
 			goto csum_error;
+		if (sk_filter(sk, skb))
+			goto drop;
 	}
 
+	udp_csum_pull_header(skb);
 	if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {
 		UDP6_INC_STATS_BH(sock_net(sk),
 				  UDP_MIB_RCVBUFERRORS, is_udplite);