6lowpan: add udp compression via nhc layer

This patch move UDP header compression and uncompression into the
generic 6LoWPAN nhc header compression layer. Moreover this patch
activates the nhc layer compression in iphc compression and
uncompression functions.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Cc: Martin Townsend <mtownsend1973@gmail.com>
Reviewed-by: Stefan Schmidt <s.schmidt@samsung.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/6lowpan/Kconfig

-config 6LOWPAN
+menuconfig 6LOWPAN
 	tristate "6LoWPAN Support"
 	depends on IPV6
 	---help---
 	  This enables IPv6 over Low power Wireless Personal Area Network -
 	  "6LoWPAN" which is supported by IEEE 802.15.4 or Bluetooth stacks.
+
+menuconfig 6LOWPAN_NHC
+	tristate "Next Header Compression Support"
+	depends on 6LOWPAN
+	default y
+	---help---
+	  Support for next header compression.
+
+if 6LOWPAN_NHC
+
+config 6LOWPAN_NHC_UDP
+	tristate "UDP Header Support"
+	default y
+	---help---
+	  6LoWPAN IPv6 UDP Header compression according to RFC6282.
+
+endif

net/6lowpan/Makefile

-obj-$(CONFIG_6LOWPAN) := 6lowpan.o
+obj-$(CONFIG_6LOWPAN) += 6lowpan.o
 
 6lowpan-y := iphc.o nhc.o
+
+#rfc6282 nhcs
+obj-$(CONFIG_6LOWPAN_NHC_UDP) += nhc_udp.o

net/6lowpan/iphc.c

@@ -54,6 +54,8 @@
 #include <net/ipv6.h>
 #include <net/af_ieee802154.h>
 
+#include "nhc.h"
+
 /* Uncompress address function for source and
  * destination address(non-multicast).
  *
@@ -224,77 +226,6 @@ static int lowpan_uncompress_multicast_daddr(struct sk_buff *skb,
 	return 0;
 }
 
-static int uncompress_udp_header(struct sk_buff *skb, struct udphdr *uh)
-{
-	bool fail;
-	u8 tmp = 0, val = 0;
-
-	fail = lowpan_fetch_skb(skb, &tmp, sizeof(tmp));
-
-	if ((tmp & LOWPAN_NHC_UDP_MASK) == LOWPAN_NHC_UDP_ID) {
-		pr_debug("UDP header uncompression\n");
-		switch (tmp & LOWPAN_NHC_UDP_CS_P_11) {
-		case LOWPAN_NHC_UDP_CS_P_00:
-			fail |= lowpan_fetch_skb(skb, &uh->source,
-						 sizeof(uh->source));
-			fail |= lowpan_fetch_skb(skb, &uh->dest,
-						 sizeof(uh->dest));
-			break;
-		case LOWPAN_NHC_UDP_CS_P_01:
-			fail |= lowpan_fetch_skb(skb, &uh->source,
-						 sizeof(uh->source));
-			fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
-			uh->dest = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
-			break;
-		case LOWPAN_NHC_UDP_CS_P_10:
-			fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
-			uh->source = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
-			fail |= lowpan_fetch_skb(skb, &uh->dest,
-						 sizeof(uh->dest));
-			break;
-		case LOWPAN_NHC_UDP_CS_P_11:
-			fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
-			uh->source = htons(LOWPAN_NHC_UDP_4BIT_PORT +
-					   (val >> 4));
-			uh->dest = htons(LOWPAN_NHC_UDP_4BIT_PORT +
-					 (val & 0x0f));
-			break;
-		default:
-			pr_debug("ERROR: unknown UDP format\n");
-			goto err;
-		}
-
-		pr_debug("uncompressed UDP ports: src = %d, dst = %d\n",
-			 ntohs(uh->source), ntohs(uh->dest));
-
-		/* checksum */
-		if (tmp & LOWPAN_NHC_UDP_CS_C) {
-			pr_debug_ratelimited("checksum elided currently not supported\n");
-			goto err;
-		} else {
-			fail |= lowpan_fetch_skb(skb, &uh->check,
-						 sizeof(uh->check));
-		}
-
-		/* UDP length needs to be infered from the lower layers
-		 * here, we obtain the hint from the remaining size of the
-		 * frame
-		 */
-		uh->len = htons(skb->len + sizeof(struct udphdr));
-		pr_debug("uncompressed UDP length: src = %d", ntohs(uh->len));
-	} else {
-		pr_debug("ERROR: unsupported NH format\n");
-		goto err;
-	}
-
-	if (fail)
-		goto err;
-
-	return 0;
-err:
-	return -EINVAL;
-}
-
 /* TTL uncompression values */
 static const u8 lowpan_ttl_values[] = { 0, 1, 64, 255 };
 
@@ -425,29 +356,11 @@ lowpan_header_decompress(struct sk_buff *skb, struct net_device *dev,
 			return -EINVAL;
 	}
 
-	/* UDP data uncompression */
+	/* Next header data uncompression */
 	if (iphc0 & LOWPAN_IPHC_NH_C) {
-		struct udphdr uh;
-		const int needed = sizeof(struct udphdr) + sizeof(hdr);
-
-		if (uncompress_udp_header(skb, &uh))
-			return -EINVAL;
-
-		/* replace the compressed UDP head by the uncompressed UDP
-		 * header
-		 */
-		err = skb_cow(skb, needed);
-		if (unlikely(err))
+		err = lowpan_nhc_do_uncompression(skb, dev, &hdr);
+		if (err < 0)
 			return err;
-
-		skb_push(skb, sizeof(struct udphdr));
-		skb_reset_transport_header(skb);
-		skb_copy_to_linear_data(skb, &uh, sizeof(struct udphdr));
-
-		raw_dump_table(__func__, "raw UDP header dump",
-			       (u8 *)&uh, sizeof(uh));
-
-		hdr.nexthdr = UIP_PROTO_UDP;
 	} else {
 		err = skb_cow(skb, sizeof(hdr));
 		if (unlikely(err))
@@ -500,71 +413,6 @@ static u8 lowpan_compress_addr_64(u8 **hc_ptr, u8 shift,
 	return rol8(val, shift);
 }
 
-static void compress_udp_header(u8 **hc_ptr, struct sk_buff *skb)
-{
-	struct udphdr *uh;
-	u8 tmp;
-
-	/* In the case of RAW sockets the transport header is not set by
-	 * the ip6 stack so we must set it ourselves
-	 */
-	if (skb->transport_header == skb->network_header)
-		skb_set_transport_header(skb, sizeof(struct ipv6hdr));
-
-	uh = udp_hdr(skb);
-
-	if (((ntohs(uh->source) & LOWPAN_NHC_UDP_4BIT_MASK) ==
-	     LOWPAN_NHC_UDP_4BIT_PORT) &&
-	    ((ntohs(uh->dest) & LOWPAN_NHC_UDP_4BIT_MASK) ==
-	     LOWPAN_NHC_UDP_4BIT_PORT)) {
-		pr_debug("UDP header: both ports compression to 4 bits\n");
-		/* compression value */
-		tmp = LOWPAN_NHC_UDP_CS_P_11;
-		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
-		/* source and destination port */
-		tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_4BIT_PORT +
-		      ((ntohs(uh->source) - LOWPAN_NHC_UDP_4BIT_PORT) << 4);
-		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
-	} else if ((ntohs(uh->dest) & LOWPAN_NHC_UDP_8BIT_MASK) ==
-			LOWPAN_NHC_UDP_8BIT_PORT) {
-		pr_debug("UDP header: remove 8 bits of dest\n");
-		/* compression value */
-		tmp = LOWPAN_NHC_UDP_CS_P_01;
-		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
-		/* source port */
-		lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
-		/* destination port */
-		tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_8BIT_PORT;
-		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
-	} else if ((ntohs(uh->source) & LOWPAN_NHC_UDP_8BIT_MASK) ==
-			LOWPAN_NHC_UDP_8BIT_PORT) {
-		pr_debug("UDP header: remove 8 bits of source\n");
-		/* compression value */
-		tmp = LOWPAN_NHC_UDP_CS_P_10;
-		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
-		/* source port */
-		tmp = ntohs(uh->source) - LOWPAN_NHC_UDP_8BIT_PORT;
-		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
-		/* destination port */
-		lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
-	} else {
-		pr_debug("UDP header: can't compress\n");
-		/* compression value */
-		tmp = LOWPAN_NHC_UDP_CS_P_00;
-		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
-		/* source port */
-		lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
-		/* destination port */
-		lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
-	}
-
-	/* checksum is always inline */
-	lowpan_push_hc_data(hc_ptr, &uh->check, sizeof(uh->check));
-
-	/* skip the UDP header */
-	skb_pull(skb, sizeof(struct udphdr));
-}
-
 int lowpan_header_compress(struct sk_buff *skb, struct net_device *dev,
 			   unsigned short type, const void *_daddr,
 			   const void *_saddr, unsigned int len)
@@ -572,7 +420,7 @@ int lowpan_header_compress(struct sk_buff *skb, struct net_device *dev,
 	u8 tmp, iphc0, iphc1, *hc_ptr;
 	struct ipv6hdr *hdr;
 	u8 head[100] = {};
-	int addr_type;
+	int ret, addr_type;
 
 	if (type != ETH_P_IPV6)
 		return -EINVAL;
@@ -649,13 +497,12 @@ int lowpan_header_compress(struct sk_buff *skb, struct net_device *dev,
 
 	/* NOTE: payload length is always compressed */
 
-	/* Next Header is compress if UDP */
-	if (hdr->nexthdr == UIP_PROTO_UDP)
-		iphc0 |= LOWPAN_IPHC_NH_C;
-
-	if ((iphc0 & LOWPAN_IPHC_NH_C) == 0)
-		lowpan_push_hc_data(&hc_ptr, &hdr->nexthdr,
-				    sizeof(hdr->nexthdr));
+	/* Check if we provide the nhc format for nexthdr and compression
+	 * functionality. If not nexthdr is handled inline and not compressed.
+	 */
+	ret = lowpan_nhc_check_compression(skb, hdr, &hc_ptr, &iphc0);
+	if (ret < 0)
+		return ret;
 
 	/* Hop limit
 	 * if 1:   compress, encoding is 01
@@ -741,9 +588,12 @@ int lowpan_header_compress(struct sk_buff *skb, struct net_device *dev,
 		}
 	}
 
-	/* UDP header compression */
-	if (hdr->nexthdr == UIP_PROTO_UDP)
-		compress_udp_header(&hc_ptr, skb);
+	/* next header compression */
+	if (iphc0 & LOWPAN_IPHC_NH_C) {
+		ret = lowpan_nhc_do_compression(skb, hdr, &hc_ptr);
+		if (ret < 0)
+			return ret;
+	}
 
 	head[0] = iphc0;
 	head[1] = iphc1;
@@ -761,4 +611,12 @@ int lowpan_header_compress(struct sk_buff *skb, struct net_device *dev,
 }
 EXPORT_SYMBOL_GPL(lowpan_header_compress);
 
+static int __init lowpan_module_init(void)
+{
+	request_module_nowait("nhc_udp");
+
+	return 0;
+}
+module_init(lowpan_module_init);
+
 MODULE_LICENSE("GPL");

net/6lowpan/nhc_udp.c

+/*
+ *	6LoWPAN IPv6 UDP compression according to RFC6282
+ *
+ *
+ *	Authors:
+ *	Alexander Aring	<aar@pengutronix.de>
+ *
+ *	Orignal written by:
+ *	Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
+ *	Jon Smirl <jonsmirl@gmail.com>
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ */
+
+#include "nhc.h"
+
+#define LOWPAN_NHC_UDP_IDLEN	1
+
+static int udp_uncompress(struct sk_buff *skb, size_t needed)
+{
+	u8 tmp = 0, val = 0;
+	struct udphdr uh;
+	bool fail;
+	int err;
+
+	fail = lowpan_fetch_skb(skb, &tmp, sizeof(tmp));
+
+	pr_debug("UDP header uncompression\n");
+	switch (tmp & LOWPAN_NHC_UDP_CS_P_11) {
+	case LOWPAN_NHC_UDP_CS_P_00:
+		fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
+		fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
+		break;
+	case LOWPAN_NHC_UDP_CS_P_01:
+		fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
+		fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
+		uh.dest = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
+		break;
+	case LOWPAN_NHC_UDP_CS_P_10:
+		fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
+		uh.source = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
+		fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
+		break;
+	case LOWPAN_NHC_UDP_CS_P_11:
+		fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
+		uh.source = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val >> 4));
+		uh.dest = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val & 0x0f));
+		break;
+	default:
+		BUG();
+	}
+
+	pr_debug("uncompressed UDP ports: src = %d, dst = %d\n",
+		 ntohs(uh.source), ntohs(uh.dest));
+
+	/* checksum */
+	if (tmp & LOWPAN_NHC_UDP_CS_C) {
+		pr_debug_ratelimited("checksum elided currently not supported\n");
+		fail = true;
+	} else {
+		fail |= lowpan_fetch_skb(skb, &uh.check, sizeof(uh.check));
+	}
+
+	if (fail)
+		return -EINVAL;
+
+	/* UDP length needs to be infered from the lower layers
+	 * here, we obtain the hint from the remaining size of the
+	 * frame
+	 */
+	uh.len = htons(skb->len + sizeof(struct udphdr));
+	pr_debug("uncompressed UDP length: src = %d", ntohs(uh.len));
+
+	/* replace the compressed UDP head by the uncompressed UDP
+	 * header
+	 */
+	err = skb_cow(skb, needed);
+	if (unlikely(err))
+		return err;
+
+	skb_push(skb, sizeof(struct udphdr));
+	skb_copy_to_linear_data(skb, &uh, sizeof(struct udphdr));
+
+	return 0;
+}
+
+static int udp_compress(struct sk_buff *skb, u8 **hc_ptr)
+{
+	const struct udphdr *uh = udp_hdr(skb);
+	u8 tmp;
+
+	if (((ntohs(uh->source) & LOWPAN_NHC_UDP_4BIT_MASK) ==
+	     LOWPAN_NHC_UDP_4BIT_PORT) &&
+	    ((ntohs(uh->dest) & LOWPAN_NHC_UDP_4BIT_MASK) ==
+	     LOWPAN_NHC_UDP_4BIT_PORT)) {
+		pr_debug("UDP header: both ports compression to 4 bits\n");
+		/* compression value */
+		tmp = LOWPAN_NHC_UDP_CS_P_11;
+		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
+		/* source and destination port */
+		tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_4BIT_PORT +
+		      ((ntohs(uh->source) - LOWPAN_NHC_UDP_4BIT_PORT) << 4);
+		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
+	} else if ((ntohs(uh->dest) & LOWPAN_NHC_UDP_8BIT_MASK) ==
+			LOWPAN_NHC_UDP_8BIT_PORT) {
+		pr_debug("UDP header: remove 8 bits of dest\n");
+		/* compression value */
+		tmp = LOWPAN_NHC_UDP_CS_P_01;
+		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
+		/* source port */
+		lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
+		/* destination port */
+		tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_8BIT_PORT;
+		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
+	} else if ((ntohs(uh->source) & LOWPAN_NHC_UDP_8BIT_MASK) ==
+			LOWPAN_NHC_UDP_8BIT_PORT) {
+		pr_debug("UDP header: remove 8 bits of source\n");
+		/* compression value */
+		tmp = LOWPAN_NHC_UDP_CS_P_10;
+		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
+		/* source port */
+		tmp = ntohs(uh->source) - LOWPAN_NHC_UDP_8BIT_PORT;
+		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
+		/* destination port */
+		lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
+	} else {
+		pr_debug("UDP header: can't compress\n");
+		/* compression value */
+		tmp = LOWPAN_NHC_UDP_CS_P_00;
+		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
+		/* source port */
+		lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
+		/* destination port */
+		lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
+	}
+
+	/* checksum is always inline */
+	lowpan_push_hc_data(hc_ptr, &uh->check, sizeof(uh->check));
+
+	return 0;
+}
+
+static void udp_nhid_setup(struct lowpan_nhc *nhc)
+{
+	nhc->id[0] = LOWPAN_NHC_UDP_ID;
+	nhc->idmask[0] = LOWPAN_NHC_UDP_MASK;
+}
+
+LOWPAN_NHC(nhc_udp, "RFC6282 UDP", NEXTHDR_UDP, sizeof(struct udphdr),
+	   udp_nhid_setup, LOWPAN_NHC_UDP_IDLEN, udp_uncompress, udp_compress);
+
+module_lowpan_nhc(nhc_udp);
+MODULE_DESCRIPTION("6LoWPAN next header RFC6282 UDP compression");
+MODULE_LICENSE("GPL");