datagram: Add offset argument to __skb_recv_datagram

This one is only considered for MSG_PEEK flag and the value pointed by
it specifies where to start peeking bytes from. If the offset happens to
point into the middle of the returned skb, the offset within this skb is
put back to this very argument.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2b7317ff297f67ef2e623ec7a6b1ea564c2614d1..f3cf43de3c2a31eaa134a4f3d49472ada01b9a81 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2046,7 +2046,7 @@ static inline void skb_frag_add_head(struct sk_buff *skb, struct sk_buff *frag)
        for (iter = skb_shinfo(skb)->frag_list; iter; iter = iter->next)
 
 extern struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
-                                          int *peeked, int *err);
+                                          int *peeked, int *off, int *err);
 extern struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags,
                                         int noblock, int *err);
 extern unsigned int    datagram_poll(struct file *file, struct socket *sock,

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 6f54d0a17f8e6baa7098bcc5ac0fede07307b399..d3cf12f62c8f213fc2c2a33797c1749f1d18be88 100644 (file)
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -132,6 +132,8 @@ out_noerr:
  *     __skb_recv_datagram - Receive a datagram skbuff
  *     @sk: socket
  *     @flags: MSG_ flags
+ *     @off: an offset in bytes to peek skb from. Returns an offset
+ *           within an skb where data actually starts
  *     @peeked: returns non-zero if this packet has been seen before
  *     @err: error code returned
  *
@@ -158,7 +160,7 @@ out_noerr:
  *     the standard around please.
  */
 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
-                                   int *peeked, int *err)
+                                   int *peeked, int *off, int *err)
 {
        struct sk_buff *skb;
        long timeo;
@@ -183,19 +185,22 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
                struct sk_buff_head *queue = &sk->sk_receive_queue;
 
                spin_lock_irqsave(&queue->lock, cpu_flags);
-               skb = skb_peek(queue);
-               if (skb) {
+               skb_queue_walk(queue, skb) {
                        *peeked = skb->peeked;
                        if (flags & MSG_PEEK) {
+                               if (*off >= skb->len) {
+                                       *off -= skb->len;
+                                       continue;
+                               }
                                skb->peeked = 1;
                                atomic_inc(&skb->users);
                        } else
                                __skb_unlink(skb, queue);
-               }
-               spin_unlock_irqrestore(&queue->lock, cpu_flags);
 
-               if (skb)
+                       spin_unlock_irqrestore(&queue->lock, cpu_flags);
                        return skb;
+               }
+               spin_unlock_irqrestore(&queue->lock, cpu_flags);
 
                /* User doesn't want to wait */
                error = -EAGAIN;
@@ -215,10 +220,10 @@ EXPORT_SYMBOL(__skb_recv_datagram);
 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags,
                                  int noblock, int *err)
 {
-       int peeked;
+       int peeked, off = 0;
 
        return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
-                                  &peeked, err);
+                                  &peeked, &off, err);
 }
 EXPORT_SYMBOL(skb_recv_datagram);
 

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index cd99f1a0f59f5f5ccb68cfa9f41da9f7231f0247..7c41ab84e72e70c7d40c0ca968b84aa81ed1638a 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1167,7 +1167,7 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
        struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
        struct sk_buff *skb;
        unsigned int ulen, copied;
-       int peeked;
+       int peeked, off = 0;
        int err;
        int is_udplite = IS_UDPLITE(sk);
        bool slow;
@@ -1183,7 +1183,7 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 
 try_again:
        skb = __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
-                                 &peeked, &err);
+                                 &peeked, &off, &err);
        if (!skb)
                goto out;
 

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 8aebf8f90436b2f9b77e3bb964396150dc4fa6e8..37b0699e95e5331dffb186f6971411d2d16c88c8 100644 (file)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -342,7 +342,7 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
        struct inet_sock *inet = inet_sk(sk);
        struct sk_buff *skb;
        unsigned int ulen, copied;
-       int peeked;
+       int peeked, off = 0;
        int err;
        int is_udplite = IS_UDPLITE(sk);
        int is_udp4;
@@ -359,7 +359,7 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 
 try_again:
        skb = __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
-                                 &peeked, &err);
+                                 &peeked, &off, &err);
        if (!skb)
                goto out;