6LoWPAN: UDP header compression

This patch adds support for UDP header compression.
Derived from Contiki OS.

Signed-off-by: Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 47 insertions, 4 deletions

diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
index 39ec6e018227..9bf82d72bb9e 100644
--- a/net/ieee802154/6lowpan.c
+++ b/net/ieee802154/6lowpan.c
@@ -246,6 +246,50 @@ lowpan_uncompress_addr(struct sk_buff *skb, struct in6_addr *ipaddr,
         return 0;
 }
 
+static void
+lowpan_compress_udp_header(u8 **hc06_ptr, struct sk_buff *skb)
+{
+        struct udphdr *uh = udp_hdr(skb);
+
+        pr_debug("(%s): UDP header compression\n", __func__);
+
+        if (((uh->source & LOWPAN_NHC_UDP_4BIT_MASK) ==
+                                LOWPAN_NHC_UDP_4BIT_PORT) &&
+            ((uh->dest & LOWPAN_NHC_UDP_4BIT_MASK) ==
+                                LOWPAN_NHC_UDP_4BIT_PORT)) {
+                pr_debug("(%s): both ports compression to 4 bits\n", __func__);
+                **hc06_ptr = LOWPAN_NHC_UDP_CS_P_11;
+                **(hc06_ptr + 1) = /* subtraction is faster */
+                   (u8)((uh->dest - LOWPAN_NHC_UDP_4BIT_PORT) +
+                       ((uh->source & LOWPAN_NHC_UDP_4BIT_PORT) << 4));
+                *hc06_ptr += 2;
+        } else if ((uh->dest & LOWPAN_NHC_UDP_8BIT_MASK) ==
+                        LOWPAN_NHC_UDP_8BIT_PORT) {
+                pr_debug("(%s): remove 8 bits of dest\n", __func__);
+                **hc06_ptr = LOWPAN_NHC_UDP_CS_P_01;
+                memcpy(*hc06_ptr + 1, &uh->source, 2);
+                **(hc06_ptr + 3) = (u8)(uh->dest - LOWPAN_NHC_UDP_8BIT_PORT);
+                *hc06_ptr += 4;
+        } else if ((uh->source & LOWPAN_NHC_UDP_8BIT_MASK) ==
+                        LOWPAN_NHC_UDP_8BIT_PORT) {
+                pr_debug("(%s): remove 8 bits of source\n", __func__);
+                **hc06_ptr = LOWPAN_NHC_UDP_CS_P_10;
+                memcpy(*hc06_ptr + 1, &uh->dest, 2);
+                **(hc06_ptr + 3) = (u8)(uh->source - LOWPAN_NHC_UDP_8BIT_PORT);
+                *hc06_ptr += 4;
+        } else {
+                pr_debug("(%s): can't compress header\n", __func__);
+                **hc06_ptr = LOWPAN_NHC_UDP_CS_P_00;
+                memcpy(*hc06_ptr + 1, &uh->source, 2);
+                memcpy(*hc06_ptr + 3, &uh->dest, 2);
+                *hc06_ptr += 5;
+        }
+
+        /* checksum is always inline */
+        memcpy(*hc06_ptr, &uh->check, 2);
+        *hc06_ptr += 2;
+}
+
 static u8 lowpan_fetch_skb_u8(struct sk_buff *skb)
 {
         u8 ret;
@@ -365,8 +409,6 @@ static int lowpan_header_create(struct sk_buff *skb,
         if (hdr->nexthdr == UIP_PROTO_UDP)
                 iphc0 |= LOWPAN_IPHC_NH_C;
 
-/* TODO: next header compression */
-
         if ((iphc0 & LOWPAN_IPHC_NH_C) == 0) {
                 *hc06_ptr = hdr->nexthdr;
                 hc06_ptr += 1;
@@ -454,8 +496,9 @@ static int lowpan_header_create(struct sk_buff *skb,
                 }
         }
 
-        /* TODO: UDP header compression */
-        /* TODO: Next Header compression */
+        /* UDP header compression */
+        if (hdr->nexthdr == UIP_PROTO_UDP)
+                lowpan_compress_udp_header(&hc06_ptr, skb);
 
         head[0] = iphc0;
         head[1] = iphc1;