Merge branch 'udp-peek'

Willem de Bruijn says:

====================
udp: support SO_PEEK_OFF

Support peeking at a non-zero offset for UDP sockets. Match the
existing behavior on Unix datagram sockets.

1/3 makes the sk_peek_offset functions safe to use outside locks
2/3 removes udp headers before enqueue, to simplify offset arithmetic
3/3 introduces SO_PEEK_OFFSET support, with Unix socket peek semantics.

Changes
  v1->v2
    - squash patches 3 and 4
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 31 insertions, 12 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 15d0df943466..007381270ff8 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2949,7 +2949,12 @@ int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
 				 struct iov_iter *from, int len);
 int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *frm);
 void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
-void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb);
+void __skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb, int len);
+static inline void skb_free_datagram_locked(struct sock *sk,
+					    struct sk_buff *skb)
+{
+	__skb_free_datagram_locked(sk, skb, 0);
+}
 int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags);
 int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len);
 int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len);
diff --git a/include/net/sock.h b/include/net/sock.h
index 310c4367ea83..1decb7a22261 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -457,28 +457,32 @@ struct sock {
 #define SK_CAN_REUSE	1
 #define SK_FORCE_REUSE	2
 
+int sk_set_peek_off(struct sock *sk, int val);
+
 static inline int sk_peek_offset(struct sock *sk, int flags)
 {
-	if ((flags & MSG_PEEK) && (sk->sk_peek_off >= 0))
-		return sk->sk_peek_off;
-	else
-		return 0;
+	if (unlikely(flags & MSG_PEEK)) {
+		s32 off = READ_ONCE(sk->sk_peek_off);
+		if (off >= 0)
+			return off;
+	}
+
+	return 0;
 }
 
 static inline void sk_peek_offset_bwd(struct sock *sk, int val)
 {
-	if (sk->sk_peek_off >= 0) {
-		if (sk->sk_peek_off >= val)
-			sk->sk_peek_off -= val;
-		else
-			sk->sk_peek_off = 0;
+	s32 off = READ_ONCE(sk->sk_peek_off);
+
+	if (unlikely(off >= 0)) {
+		off = max_t(s32, off - val, 0);
+		WRITE_ONCE(sk->sk_peek_off, off);
 	}
 }
 
 static inline void sk_peek_offset_fwd(struct sock *sk, int val)
 {
-	if (sk->sk_peek_off >= 0)
-		sk->sk_peek_off += val;
+	sk_peek_offset_bwd(sk, -val);
 }
 
 /*
@@ -1862,6 +1866,7 @@ 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);
diff --git a/include/net/udp.h b/include/net/udp.h
index d870ec1611c4..a0b0da97164c 100644
--- a/include/net/udp.h
+++ b/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);