tipc: rename and move message reassembly function

The function tipc_link_frag_rcv() is in reality a re-entrant generic
message reassemby function that has nothing in particular to do with
the link, where it is defined now. This becomes obvious when we see
the need to call the function from other places in the code.

In this commit rename it to tipc_buf_append() and move it to the file
msg.c. We also simplify its signature by moving the tail pointer to
the control block of the head buffer, hence making the head buffer
self-contained.

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

1 files changed, 54 insertions, 1 deletions

diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index e525f8ce1de..8be6e94a1ca 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -1,7 +1,7 @@
 /*
  * net/tipc/msg.c: TIPC message header routines
  *
- * Copyright (c) 2000-2006, Ericsson AB
+ * Copyright (c) 2000-2006, 2014, Ericsson AB
  * Copyright (c) 2005, 2010-2011, Wind River Systems
  * All rights reserved.
  *
@@ -99,3 +99,56 @@ int tipc_msg_build(struct tipc_msg *hdr, struct iovec const *msg_sect,
 	}
 	return dsz;
 }
+
+/* tipc_buf_append(): Append a buffer to the fragment list of another buffer
+ * Let first buffer become head buffer
+ * Returns 1 and sets *buf to headbuf if chain is complete, otherwise 0
+ * Leaves headbuf pointer at NULL if failure
+ */
+int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf)
+{
+	struct sk_buff *head = *headbuf;
+	struct sk_buff *frag = *buf;
+	struct sk_buff *tail;
+	struct tipc_msg *msg = buf_msg(frag);
+	u32 fragid = msg_type(msg);
+	bool headstolen;
+	int delta;
+
+	skb_pull(frag, msg_hdr_sz(msg));
+
+	if (fragid == FIRST_FRAGMENT) {
+		if (head || skb_unclone(frag, GFP_ATOMIC))
+			goto out_free;
+		head = *headbuf = frag;
+		skb_frag_list_init(head);
+		return 0;
+	}
+	if (!head)
+		goto out_free;
+	tail = TIPC_SKB_CB(head)->tail;
+	if (skb_try_coalesce(head, frag, &headstolen, &delta)) {
+		kfree_skb_partial(frag, headstolen);
+	} else {
+		if (!skb_has_frag_list(head))
+			skb_shinfo(head)->frag_list = frag;
+		else
+			tail->next = frag;
+		head->truesize += frag->truesize;
+		head->data_len += frag->len;
+		head->len += frag->len;
+		TIPC_SKB_CB(head)->tail = frag;
+	}
+	if (fragid == LAST_FRAGMENT) {
+		*buf = head;
+		TIPC_SKB_CB(head)->tail = NULL;
+		*headbuf = NULL;
+		return 1;
+	}
+	*buf = NULL;
+	return 0;
+out_free:
+	pr_warn_ratelimited("Unable to build fragment list\n");
+	kfree_skb(*buf);
+	return 0;
+}