From 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 Mon Sep 17 00:00:00 2001 From: Sam Protsenko Date: Thu, 20 Dec 2018 20:29:20 +0200 Subject: ppp: Move PFC decompression to PPP generic layer Extract "Protocol" field decompression code from transport protocols to PPP generic layer, where it actually belongs. As a consequence, this patch fixes incorrect place of PFC decompression in L2TP driver (when it's not PPPOX_BOUND) and also enables this decompression for other protocols, like PPPoE. Protocol field decompression also happens in PPP Multilink Protocol code and in PPP compression protocols implementations (bsd, deflate, mppe). It looks like there is no easy way to get rid of that, so it was decided to leave it as is, but provide those cases with appropriate comments instead. Changes in v2: - Fix the order of checking skb data room and proto decompression - Remove "inline" keyword from ppp_decompress_proto() - Don't split line before function name - Prefix ppp_decompress_proto() function with "__" - Add ppp_decompress_proto() function with skb data room checks - Add description for introduced functions - Fix comments (as per review on mailing list) Signed-off-by: Sam Protsenko Reviewed-by: Guillaume Nault Signed-off-by: David S. Miller --- drivers/net/ppp/ppp_generic.c | 54 ++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 51 insertions(+), 3 deletions(-) (limited to 'drivers/net/ppp/ppp_generic.c') diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 500bc0027c1b..c708400fff4a 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -1965,6 +1965,46 @@ ppp_do_recv(struct ppp *ppp, struct sk_buff *skb, struct channel *pch) ppp_recv_unlock(ppp); } +/** + * __ppp_decompress_proto - Decompress protocol field, slim version. + * @skb: Socket buffer where protocol field should be decompressed. It must have + * at least 1 byte of head room and 1 byte of linear data. First byte of + * data must be a protocol field byte. + * + * Decompress protocol field in PPP header if it's compressed, e.g. when + * Protocol-Field-Compression (PFC) was negotiated. No checks w.r.t. skb data + * length are done in this function. + */ +static void __ppp_decompress_proto(struct sk_buff *skb) +{ + if (skb->data[0] & 0x01) + *(u8 *)skb_push(skb, 1) = 0x00; +} + +/** + * ppp_decompress_proto - Check skb data room and decompress protocol field. + * @skb: Socket buffer where protocol field should be decompressed. First byte + * of data must be a protocol field byte. + * + * Decompress protocol field in PPP header if it's compressed, e.g. when + * Protocol-Field-Compression (PFC) was negotiated. This function also makes + * sure that skb data room is sufficient for Protocol field, before and after + * decompression. + * + * Return: true - decompressed successfully, false - not enough room in skb. + */ +static bool ppp_decompress_proto(struct sk_buff *skb) +{ + /* At least one byte should be present (if protocol is compressed) */ + if (!pskb_may_pull(skb, 1)) + return false; + + __ppp_decompress_proto(skb); + + /* Protocol field should occupy 2 bytes when not compressed */ + return pskb_may_pull(skb, 2); +} + void ppp_input(struct ppp_channel *chan, struct sk_buff *skb) { @@ -1977,7 +2017,7 @@ ppp_input(struct ppp_channel *chan, struct sk_buff *skb) } read_lock_bh(&pch->upl); - if (!pskb_may_pull(skb, 2)) { + if (!ppp_decompress_proto(skb)) { kfree_skb(skb); if (pch->ppp) { ++pch->ppp->dev->stats.rx_length_errors; @@ -2074,6 +2114,9 @@ ppp_receive_nonmp_frame(struct ppp *ppp, struct sk_buff *skb) if (ppp->flags & SC_MUST_COMP && ppp->rstate & SC_DC_FERROR) goto err; + /* At this point the "Protocol" field MUST be decompressed, either in + * ppp_input(), ppp_decompress_frame() or in ppp_receive_mp_frame(). + */ proto = PPP_PROTO(skb); switch (proto) { case PPP_VJC_COMP: @@ -2245,6 +2288,9 @@ ppp_decompress_frame(struct ppp *ppp, struct sk_buff *skb) skb_put(skb, len); skb_pull(skb, 2); /* pull off the A/C bytes */ + /* Don't call __ppp_decompress_proto() here, but instead rely on + * corresponding algo (mppe/bsd/deflate) to decompress it. + */ } else { /* Uncompressed frame - pass to decompressor so it can update its dictionary if necessary. */ @@ -2290,9 +2336,11 @@ ppp_receive_mp_frame(struct ppp *ppp, struct sk_buff *skb, struct channel *pch) /* * Do protocol ID decompression on the first fragment of each packet. + * We have to do that here, because ppp_receive_nonmp_frame() expects + * decompressed protocol field. */ - if ((PPP_MP_CB(skb)->BEbits & B) && (skb->data[0] & 1)) - *(u8 *)skb_push(skb, 1) = 0; + if (PPP_MP_CB(skb)->BEbits & B) + __ppp_decompress_proto(skb); /* * Expand sequence number to 32 bits, making it as close -- cgit v1.2.3-59-g8ed1b