From d39cd5e99a0ad88aba6793fb5e5f34e29cda6e6f Mon Sep 17 00:00:00 2001 From: stephen hemminger Date: Mon, 20 Dec 2010 17:58:33 +0000 Subject: [PATCH] ppp: allow disabling multilink protocol ID compression Linux would not connect to other router running old version Cisco IOS (12.0). This is most likely a bug in that version of IOS, since it is fixed in later versions. As a workaround this patch allows a module parameter to be set to disable compressing the protocol ID. See: https://bugzilla.vyatta.com/show_bug.cgi?id=3979 RFC 1990 allows an implementation to formulate MP fragments as if protocol compression had been negotiated. This allows us to always send compressed protocol IDs. But some implementations don't accept MP fragments with compressed protocol IDs. This parameter allows us to interoperate with them. The default value of the configurable parameter is the same as the current behavior: protocol compression is enabled. If protocol compression is disabled we will not send compressed protocol IDs. This is based on an earlier patch by Bob Gilligan (using a sysctl). Module parameter is writable to allow for enabling even if ppp is already loaded for other uses. Signed-off-by: Stephen Hemminger Acked-by: Eric Dumazet Acked-by: Paul Mackerras Signed-off-by: David S. Miller --- drivers/net/ppp_generic.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c index 39659976a1ac..89294b43c4a9 100644 --- a/drivers/net/ppp_generic.c +++ b/drivers/net/ppp_generic.c @@ -1285,6 +1285,11 @@ ppp_push(struct ppp *ppp) } #ifdef CONFIG_PPP_MULTILINK +static bool mp_protocol_compress __read_mostly = true; +module_param(mp_protocol_compress, bool, S_IRUGO | S_IWUSR); +MODULE_PARM_DESC(mp_protocol_compress, + "compress protocol id in multilink fragments"); + /* * Divide a packet to be transmitted into fragments and * send them out the individual links. @@ -1347,10 +1352,10 @@ static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb) if (nfree == 0 || nfree < navail / 2) return 0; /* can't take now, leave it in xmit_pending */ - /* Do protocol field compression (XXX this should be optional) */ + /* Do protocol field compression */ p = skb->data; len = skb->len; - if (*p == 0) { + if (*p == 0 && mp_protocol_compress) { ++p; --len; }