ieee820154: 6lowpan: dispatch evaluation rework

This patch complete reworks the evaluation of 6lowpan dispatch value by
introducing a receive handler mechanism for each dispatch value.

A list of changes:

 - Doing uncompression on-the-fly when FRAG1 is received, this require
   some special handling for 802.15.4 lltype in generic 6lowpan branch
   for setting the payload length correct.
 - Fix dispatch mask for fragmentation.
 - Add IPv6 dispatch evaluation for FRAG1.
 - Add skb_unshare for dispatch which might manipulate the skb data
   buffer.

Cc: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 127 insertions, 61 deletions

diff --git a/net/ieee802154/6lowpan/rx.c b/net/ieee802154/6lowpan/rx.c
index f9cb70b6749f..fded1099fae0 100644
--- a/net/ieee802154/6lowpan/rx.c
+++ b/net/ieee802154/6lowpan/rx.c
@@ -15,8 +15,9 @@
 
 #include "6lowpan_i.h"
 
-static int lowpan_give_skb_to_device(struct sk_buff *skb,
-				     struct net_device *wdev)
+#define LOWPAN_DISPATCH_FRAG_MASK	0xf8
+
+static int lowpan_give_skb_to_device(struct sk_buff *skb)
 {
 	skb->protocol = htons(ETH_P_IPV6);
 	skb->pkt_type = PACKET_HOST;
@@ -24,21 +25,77 @@ static int lowpan_give_skb_to_device(struct sk_buff *skb,
 	return netif_rx(skb);
 }
 
-static int
-iphc_decompress(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
+static int lowpan_rx_handlers_result(struct sk_buff *skb, lowpan_rx_result res)
+{
+	switch (res) {
+	case RX_CONTINUE:
+		/* nobody cared about this packet */
+		net_warn_ratelimited("%s: received unknown dispatch\n",
+				     __func__);
+
+		/* fall-through */
+	case RX_DROP_UNUSABLE:
+		kfree_skb(skb);
+
+		/* fall-through */
+	case RX_DROP:
+		return NET_RX_DROP;
+	case RX_QUEUED:
+		return lowpan_give_skb_to_device(skb);
+	default:
+		break;
+	}
+
+	return NET_RX_DROP;
+}
+
+static inline bool lowpan_is_frag1(u8 dispatch)
+{
+	return (dispatch & LOWPAN_DISPATCH_FRAG_MASK) == LOWPAN_DISPATCH_FRAG1;
+}
+
+static inline bool lowpan_is_fragn(u8 dispatch)
+{
+	return (dispatch & LOWPAN_DISPATCH_FRAG_MASK) == LOWPAN_DISPATCH_FRAGN;
+}
+
+static lowpan_rx_result lowpan_rx_h_frag(struct sk_buff *skb)
+{
+	int ret;
+
+	if (!(lowpan_is_frag1(*skb_network_header(skb)) ||
+	      lowpan_is_fragn(*skb_network_header(skb))))
+		return RX_CONTINUE;
+
+	ret = lowpan_frag_rcv(skb, *skb_network_header(skb) &
+			      LOWPAN_DISPATCH_FRAG_MASK);
+	if (ret == 1)
+		return RX_QUEUED;
+
+	/* Packet is freed by lowpan_frag_rcv on error or put into the frag
+	 * bucket.
+	 */
+	return RX_DROP;
+}
+
+int lowpan_iphc_decompress(struct sk_buff *skb)
 {
-	u8 iphc0, iphc1;
 	struct ieee802154_addr_sa sa, da;
+	struct ieee802154_hdr hdr;
+	u8 iphc0, iphc1;
 	void *sap, *dap;
 
+	if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
+		return -EINVAL;
+
 	raw_dump_table(__func__, "raw skb data dump", skb->data, skb->len);
 
 	if (lowpan_fetch_skb_u8(skb, &iphc0) ||
 	    lowpan_fetch_skb_u8(skb, &iphc1))
 		return -EINVAL;
 
-	ieee802154_addr_to_sa(&sa, &hdr->source);
-	ieee802154_addr_to_sa(&da, &hdr->dest);
+	ieee802154_addr_to_sa(&sa, &hdr.source);
+	ieee802154_addr_to_sa(&da, &hdr.dest);
 
 	if (sa.addr_type == IEEE802154_ADDR_SHORT)
 		sap = &sa.short_addr;
@@ -55,78 +112,87 @@ iphc_decompress(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
 					IEEE802154_ADDR_LEN, iphc0, iphc1);
 }
 
+static lowpan_rx_result lowpan_rx_h_iphc(struct sk_buff *skb)
+{
+	int ret;
+
+	if (!lowpan_is_iphc(*skb_network_header(skb)))
+		return RX_CONTINUE;
+
+	/* Setting datagram_offset to zero indicates non frag handling
+	 * while doing lowpan_header_decompress.
+	 */
+	lowpan_802154_cb(skb)->d_size = 0;
+
+	ret = lowpan_iphc_decompress(skb);
+	if (ret < 0)
+		return RX_DROP_UNUSABLE;
+
+	return RX_QUEUED;
+}
+
+lowpan_rx_result lowpan_rx_h_ipv6(struct sk_buff *skb)
+{
+	if (!lowpan_is_ipv6(*skb_network_header(skb)))
+		return RX_CONTINUE;
+
+	/* Pull off the 1-byte of 6lowpan header. */
+	skb_pull(skb, 1);
+	return RX_QUEUED;
+}
+
+static int lowpan_invoke_rx_handlers(struct sk_buff *skb)
+{
+	lowpan_rx_result res;
+
+#define CALL_RXH(rxh)			\
+	do {				\
+		res = rxh(skb);	\
+		if (res != RX_CONTINUE)	\
+			goto rxh_next;	\
+	} while (0)
+
+	/* likely at first */
+	CALL_RXH(lowpan_rx_h_iphc);
+	CALL_RXH(lowpan_rx_h_frag);
+	CALL_RXH(lowpan_rx_h_ipv6);
+
+rxh_next:
+	return lowpan_rx_handlers_result(skb, res);
+#undef CALL_RXH
+}
+
 static int lowpan_rcv(struct sk_buff *skb, struct net_device *wdev,
 		      struct packet_type *pt, struct net_device *orig_wdev)
 {
-	struct ieee802154_hdr hdr;
 	struct net_device *ldev;
-	int ret;
 
 	if (wdev->type != ARPHRD_IEEE802154 ||
 	    skb->pkt_type == PACKET_OTHERHOST)
-		goto drop;
+		return NET_RX_DROP;
 
 	ldev = wdev->ieee802154_ptr->lowpan_dev;
 	if (!ldev || !netif_running(ldev))
-		goto drop;
+		return NET_RX_DROP;
 
 	/* Replacing skb->dev and followed rx handlers will manipulate skb. */
 	skb = skb_share_check(skb, GFP_ATOMIC);
 	if (!skb)
-		goto drop;
+		return NET_RX_DROP;
 	skb->dev = ldev;
 
-	if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
-		goto drop_skb;
-
-	/* check that it's our buffer */
-	if (skb->data[0] == LOWPAN_DISPATCH_IPV6) {
-		/* Pull off the 1-byte of 6lowpan header. */
-		skb_pull(skb, 1);
-		return lowpan_give_skb_to_device(skb, wdev);
-	} else {
-		switch (skb->data[0] & 0xe0) {
-		case LOWPAN_DISPATCH_IPHC:	/* ipv6 datagram */
-			ret = iphc_decompress(skb, &hdr);
-			if (ret < 0)
-				goto drop_skb;
-
-			return lowpan_give_skb_to_device(skb, wdev);
-		case LOWPAN_DISPATCH_FRAG1:	/* first fragment header */
-			ret = lowpan_frag_rcv(skb, LOWPAN_DISPATCH_FRAG1);
-			if (ret == 1) {
-				ret = iphc_decompress(skb, &hdr);
-				if (ret < 0)
-					goto drop_skb;
-
-				return lowpan_give_skb_to_device(skb, wdev);
-			} else if (ret == -1) {
-				return NET_RX_DROP;
-			} else {
-				return NET_RX_SUCCESS;
-			}
-		case LOWPAN_DISPATCH_FRAGN:	/* next fragments headers */
-			ret = lowpan_frag_rcv(skb, LOWPAN_DISPATCH_FRAGN);
-			if (ret == 1) {
-				ret = iphc_decompress(skb, &hdr);
-				if (ret < 0)
-					goto drop_skb;
-
-				return lowpan_give_skb_to_device(skb, wdev);
-			} else if (ret == -1) {
-				return NET_RX_DROP;
-			} else {
-				return NET_RX_SUCCESS;
-			}
-		default:
-			break;
-		}
+	/* When receive frag1 it's likely that we manipulate the buffer.
+	 * When recevie iphc we manipulate the data buffer. So we need
+	 * to unshare the buffer.
+	 */
+	if (lowpan_is_frag1(*skb_network_header(skb)) ||
+	    lowpan_is_iphc(*skb_network_header(skb))) {
+		skb = skb_unshare(skb, GFP_ATOMIC);
+		if (!skb)
+			return RX_DROP;
 	}
 
-drop_skb:
-	kfree_skb(skb);
-drop:
-	return NET_RX_DROP;
+	return lowpan_invoke_rx_handlers(skb);
 }
 
 static struct packet_type lowpan_packet_type = {