Commit ef9be755 authored by Tung Nguyen's avatar Tung Nguyen Committed by David S. Miller
Browse files

tipc: eliminate buffer cloning in function tipc_msg_extract() 



The function tipc_msg_extract() is using skb_clone() to clone inner
messages from a message bundle buffer. Although this method is safe,
it has an undesired effect that each buffer clone inherits the
true-size of the bundling buffer. As a result, the buffer clone
almost always ends up with being copied anyway by the message
validation function. This makes the cloning into a sub-optimization.

In this commit we take the consequence of this realization, and copy
each inner message to a separately allocated buffer up front in the
extraction function.

As a bonus we can now eliminate the two cases where we had to copy
re-routed packets that may potentially go out on the wire again.

Signed-off-by: default avatarTung Nguyen <tung.q.nguyen@dektech.com.au>
Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9ca78674

net/tipc/msg.c

+15 −20
Original line number Diff line number Diff line
@@ -416,26 +416,31 @@ bool tipc_msg_bundle(struct sk_buff *skb, struct tipc_msg *msg, u32 mtu) 
 */

bool tipc_msg_extract(struct sk_buff *skb, struct sk_buff **iskb, int *pos)

{

	struct tipc_msg *msg;

	int imsz, offset;

	struct tipc_msg *hdr, *ihdr;

	int imsz;



	*iskb = NULL;

	if (unlikely(skb_linearize(skb)))

		goto none;



	msg = buf_msg(skb);

	offset = msg_hdr_sz(msg) + *pos;

	if (unlikely(offset > (msg_size(msg) - MIN_H_SIZE)))

	hdr = buf_msg(skb);

	if (unlikely(*pos > (msg_data_sz(hdr) - MIN_H_SIZE)))

		goto none;



	*iskb = skb_clone(skb, GFP_ATOMIC);

	if (unlikely(!*iskb))

	ihdr = (struct tipc_msg *)(msg_data(hdr) + *pos);

	imsz = msg_size(ihdr);



	if ((*pos + imsz) > msg_data_sz(hdr))

		goto none;

	skb_pull(*iskb, offset);

	imsz = msg_size(buf_msg(*iskb));

	skb_trim(*iskb, imsz);



	*iskb = tipc_buf_acquire(imsz, GFP_ATOMIC);

	if (!*iskb)

		goto none;



	skb_copy_to_linear_data(*iskb, ihdr, imsz);

	if (unlikely(!tipc_msg_validate(iskb)))

		goto none;



	*pos += align(imsz);

	return true;

none:
@@ -531,12 +536,6 @@ bool tipc_msg_reverse(u32 own_node, struct sk_buff **skb, int err) 
		msg_set_hdr_sz(hdr, BASIC_H_SIZE);

	}



	if (skb_cloned(_skb) &&

	    pskb_expand_head(_skb, BUF_HEADROOM, BUF_TAILROOM, GFP_ATOMIC))

		goto exit;



	/* reassign after skb header modifications */

	hdr = buf_msg(_skb);

	/* Now reverse the concerned fields */

	msg_set_errcode(hdr, err);

	msg_set_non_seq(hdr, 0);
@@ -595,10 +594,6 @@ bool tipc_msg_lookup_dest(struct net *net, struct sk_buff *skb, int *err) 
	if (!skb_cloned(skb))

		return true;



	/* Unclone buffer in case it was bundled */

	if (pskb_expand_head(skb, BUF_HEADROOM, BUF_TAILROOM, GFP_ATOMIC))

		return false;



	return true;

}

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