Commit a53a8b56 authored Jul 28, 2009 by Ben McKeegan Committed by David S. Miller Aug 02, 2009

ppp: fix lost fragments in ppp_mp_explode() (resubmit)



This patch fixes the corner cases where the sum of MTU of the free
channels (adjusted for fragmentation overheads) is less than the MTU
of PPP link.  There are at least 3 situations where this case might
arise:

- some of the channels are busy

- the multilink session is running in a degraded state (i.e. with less
than its full complement of active channels)

- by design, where multilink protocol is being used to artificially
increase the effective link MTU of a single link.

Without this patch, at most 1 fragment is ever sent per free channel
for a given PPP frame and any remaining part of the PPP frame that
does not fit into those fragments is silently discarded.

This patch restores the original behaviour which was broken by commit
9c705260 'ppp:ppp_mp_explode()
redesign'.  Once all 'free' channels have been given a fragment, an
additional fragment is queued to each available channel in turn, as many
times as necessary, until the entire PPP frame has been consumed.

Signed-off-by: Ben McKeegan <ben@netservers.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 0a924578

drivers/net/ppp_generic.c

+18 −16

Original line number	Diff line number	Diff line
		@@ -1384,7 +1384,7 @@ static int ppp_mp_explode(struct ppp ppp, struct sk_buff skb)

		/* create a fragment for each channel */
		bits = B;
		while (nfree > 0 && len > 0) {
		while (len > 0) {
		list = list->next;
		if (list == &ppp->channels) {
		i = 0;
		@@ -1431,6 +1431,7 @@ static int ppp_mp_explode(struct ppp ppp, struct sk_buff skb)
		*otherwise divide it according to the speed
		*of the channel we are going to transmit on
		*/
		if (nfree > 0) {
		if (pch->speed == 0) {
		flen = totlen/nfree ;
		if (nbigger > 0) {
		@@ -1447,13 +1448,14 @@ static int ppp_mp_explode(struct ppp ppp, struct sk_buff skb)
		}
		}
		nfree--;
		}

		/*
		*check if we are on the last channel or
		*we exceded the lenght of the data to
		*fragment
		*/
		if ((nfree == 0) \|\| (flen > len))
		if ((nfree <= 0) \|\| (flen > len))
		flen = len;
		/*
		*it is not worth to tx on slow channels:
		@@ -1467,7 +1469,7 @@ static int ppp_mp_explode(struct ppp ppp, struct sk_buff skb)
		continue;
		}

		mtu = pch->chan->mtu + 2 - hdrlen;
		mtu = pch->chan->mtu - hdrlen;
		if (mtu < 4)
		mtu = 4;
		if (flen > mtu)

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