tipc: extract bundled buffers by cloning instead of copying

When we currently extract a bundled buffer from a message bundle in
the function tipc_msg_extract(), we allocate a new buffer and explicitly
copy the linear data area.

This is unnecessary, since we can just clone the buffer and do
skb_pull() on the clone to move the data pointer to the correct
position.

This is what we do in this commit.

Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 28 insertions, 47 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index 8c6639d107fc..56c39b1a53a9 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -1,7 +1,7 @@
 /*
  * net/tipc/link.c: TIPC link code
  *
- * Copyright (c) 1996-2007, 2012-2014, Ericsson AB
+ * Copyright (c) 1996-2007, 2012-2015, Ericsson AB
  * Copyright (c) 2004-2007, 2010-2013, Wind River Systems
  * All rights reserved.
  *
@@ -1117,7 +1117,7 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b_ptr)
                 ackd = msg_ack(msg);
 
                 /* Release acked messages */
-                if (n_ptr->bclink.recv_permitted)
+                if (likely(n_ptr->bclink.recv_permitted))
                         tipc_bclink_acknowledge(n_ptr, msg_bcast_ack(msg));
 
                 released = 0;
@@ -1712,45 +1712,24 @@ void tipc_link_dup_queue_xmit(struct tipc_link *l_ptr,
         }
 }
 
-/**
- * buf_extract - extracts embedded TIPC message from another message
- * @skb: encapsulating message buffer
- * @from_pos: offset to extract from
- *
- * Returns a new message buffer containing an embedded message.  The
- * encapsulating buffer is left unchanged.
- */
-static struct sk_buff *buf_extract(struct sk_buff *skb, u32 from_pos)
-{
-        struct tipc_msg *msg = (struct tipc_msg *)(skb->data + from_pos);
-        u32 size = msg_size(msg);
-        struct sk_buff *eb;
-
-        eb = tipc_buf_acquire(size);
-        if (eb)
-                skb_copy_to_linear_data(eb, msg, size);
-        return eb;
-}
-
 /* tipc_link_dup_rcv(): Receive a tunnelled DUPLICATE_MSG packet.
  * Owner node is locked.
  */
-static void tipc_link_dup_rcv(struct tipc_link *l_ptr,
-                              struct sk_buff *t_buf)
+static void tipc_link_dup_rcv(struct tipc_link *link,
+                              struct sk_buff *skb)
 {
-        struct sk_buff *buf;
+        struct sk_buff *iskb;
+        int pos = 0;
 
-        if (!tipc_link_is_up(l_ptr))
+        if (!tipc_link_is_up(link))
                 return;
 
-        buf = buf_extract(t_buf, INT_H_SIZE);
-        if (buf == NULL) {
+        if (!tipc_msg_extract(skb, &iskb, &pos)) {
                 pr_warn("%sfailed to extract inner dup pkt\n", link_co_err);
                 return;
         }
-
-        /* Add buffer to deferred queue, if applicable: */
-        link_handle_out_of_seq_msg(l_ptr, buf);
+        /* Append buffer to deferred queue, if applicable: */
+        link_handle_out_of_seq_msg(link, iskb);
 }
 
 /*  tipc_link_failover_rcv(): Receive a tunnelled ORIGINAL_MSG packet
@@ -1762,6 +1741,7 @@ static struct sk_buff *tipc_link_failover_rcv(struct tipc_link *l_ptr,
         struct tipc_msg *t_msg = buf_msg(t_buf);
         struct sk_buff *buf = NULL;
         struct tipc_msg *msg;
+        int pos = 0;
 
         if (tipc_link_is_up(l_ptr))
                 tipc_link_reset(l_ptr);
@@ -1773,8 +1753,7 @@ static struct sk_buff *tipc_link_failover_rcv(struct tipc_link *l_ptr,
         /* Should there be an inner packet? */
         if (l_ptr->exp_msg_count) {
                 l_ptr->exp_msg_count--;
-                buf = buf_extract(t_buf, INT_H_SIZE);
-                if (buf == NULL) {
+                if (!tipc_msg_extract(t_buf, &buf, &pos)) {
                         pr_warn("%sno inner failover pkt\n", link_co_err);
                         goto exit;
                 }
diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index ff8c64cd1cd9..333d2ae1cf76 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -372,38 +372,40 @@ bool tipc_msg_bundle(struct sk_buff_head *list, struct sk_buff *skb, u32 mtu)
 
 /**
  *  tipc_msg_extract(): extract bundled inner packet from buffer
- *  @skb: linear outer buffer, to be extracted from.
+ *  @skb: buffer to be extracted from.
  *  @iskb: extracted inner buffer, to be returned
- *  @pos: position of msg to be extracted. Returns with pointer of next msg
+ *  @pos: position in outer message of msg to be extracted.
+ *        Returns position of next msg
  *  Consumes outer buffer when last packet extracted
  *  Returns true when when there is an extracted buffer, otherwise false
  */
 bool tipc_msg_extract(struct sk_buff *skb, struct sk_buff **iskb, int *pos)
 {
         struct tipc_msg *msg;
-        int imsz;
-        struct tipc_msg *imsg;
+        int imsz, offset;
 
+        *iskb = NULL;
         if (unlikely(skb_linearize(skb)))
-                return false;
+                goto none;
+
         msg = buf_msg(skb);
-        imsg = (struct tipc_msg *)(msg_data(msg) + *pos);
-        /* Is there space left for shortest possible message? */
-        if (*pos > (msg_data_sz(msg) - SHORT_H_SIZE))
+        offset = msg_hdr_sz(msg) + *pos;
+        if (unlikely(offset > (msg_size(msg) - MIN_H_SIZE)))
                 goto none;
-        imsz = msg_size(imsg);
 
-        /* Is there space left for current message ? */
-        if ((*pos + imsz) > msg_data_sz(msg))
+        *iskb = skb_clone(skb, GFP_ATOMIC);
+        if (unlikely(!*iskb))
                 goto none;
-        *iskb = tipc_buf_acquire(imsz);
-        if (!*iskb)
+        skb_pull(*iskb, offset);
+        imsz = msg_size(buf_msg(*iskb));
+        skb_trim(*iskb, imsz);
+        if (unlikely(!tipc_msg_validate(*iskb)))
                 goto none;
-        skb_copy_to_linear_data(*iskb, imsg, imsz);
         *pos += align(imsz);
         return true;
 none:
         kfree_skb(skb);
+        kfree_skb(*iskb);
         *iskb = NULL;
         return false;
 }