netdev - [PATCH net-next-2.6 4/8] caif: Add support for MSG

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Date:	Thu, 20 May 2010 09:44:04 +0200
From:	sjur.brandeland@...ricsson.com
To:	netdev@...r.kernel.org, davem@...emloft.net
Cc:	marcel@...tmann.org, daniel.martensson@...ricsson.com,
	linus.walleji@...ricsson.com, sjurbren@...il.com,
	Sjur Braendeland <sjur.brandeland@...ricsson.com>
Subject: [PATCH net-next-2.6 4/8] caif: Add support for MSG_TRUNC.

From: Sjur Braendeland <sjur.brandeland@...ricsson.com>

Changed handling when skb don't fit in user buffer,
instead of returning -EMSGSIZE, the buffer is truncated (just
as unix seqpakcet does).
Also MSG_TRUNC can be used to read out the actual packet size.

Signed-off-by: Sjur Braendeland <sjur.brandeland@...ricsson.com>
---
 net/caif/caif_socket.c |   42 +++++++++++++++---------------------------
 1 files changed, 15 insertions(+), 27 deletions(-)

diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 77e9956..6d33de7 100644
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -297,59 +297,47 @@ static void caif_check_flow_release(struct sock *sk)
 						CAIF_MODEMCMD_FLOW_ON_REQ);
 	}
 }
+
 /*
  * Copied from sock.c:sock_queue_rcv_skb(), and added check that user buffer
  * has sufficient size.
  */
-
 static int caif_seqpkt_recvmsg(struct kiocb *iocb, struct socket *sock,
-				struct msghdr *m, size_t buf_len, int flags)
+				struct msghdr *m, size_t len, int flags)
 
 {
 	struct sock *sk = sock->sk;
 	struct sk_buff *skb;
 	int ret = 0;
-	int len;
+	int copylen;
 
-	if (unlikely(!buf_len))
-		return -EINVAL;
+	ret = -EOPNOTSUPP;
+	if (m->msg_flags&MSG_OOB)
+		goto read_error;
 
 	skb = skb_recv_datagram(sk, flags, 0 , &ret);
 	if (!skb)
 		goto read_error;
-
-	len = skb->len;
-
-	if (skb && skb->len > buf_len && !(flags & MSG_PEEK)) {
-		len = buf_len;
-		/*
-		 * Push skb back on receive queue if buffer too small.
-		 * This has a built-in race where multi-threaded receive
-		 * may get packet in wrong order, but multiple read does
-		 * not really guarantee ordered delivery anyway.
-		 * Let's optimize for speed without taking locks.
-		 */
-
-		skb_queue_head(&sk->sk_receive_queue, skb);
-		ret = -EMSGSIZE;
-		goto read_error;
+	copylen = skb->len;
+	if (len < copylen) {
+		m->msg_flags |= MSG_TRUNC;
+		copylen = len;
 	}
 
-	ret = skb_copy_datagram_iovec(skb, 0, m->msg_iov, len);
+	ret = skb_copy_datagram_iovec(skb, 0, m->msg_iov, copylen);
 	if (ret)
-		goto read_error;
+		goto out_free;
 
+	ret = (flags & MSG_TRUNC) ? skb->len : copylen;
+out_free:
 	skb_free_datagram(sk, skb);
-
 	caif_check_flow_release(sk);
-
-	return len;
+	return ret;
 
 read_error:
 	return ret;
 }
 
-
 /* Copied from unix_stream_wait_data, identical except for lock call. */
 static long caif_stream_data_wait(struct sock *sk, long timeo)
 {
-- 
1.6.3.3

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