[Linux-zigbee-devel] [PATCH 4/6] [6LoWPAN] UDP header compression

[Alexander Smirnov]

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

Signed-off-by: Alexander Smirnov <alex.bluesman.smir...@gmail.com>
---
 net/ieee802154/6lowpan.c |   51 ++++++++++++++++++++++++++++++++++++++++++---
 net/ieee802154/6lowpan.h |    5 ++++
 2 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
index c4aae4e..6da3357 100644
--- a/net/ieee802154/6lowpan.c
+++ b/net/ieee802154/6lowpan.c
@@ -365,8 +365,6 @@ 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 +452,53 @@ 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) {
+               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;
+       }
+
+       /* TODO: other NH types support? */
 
        head[0] = iphc0;
        head[1] = iphc1;
diff --git a/net/ieee802154/6lowpan.h b/net/ieee802154/6lowpan.h
index 5d2e5a0..aeff3f3 100644
--- a/net/ieee802154/6lowpan.h
+++ b/net/ieee802154/6lowpan.h
@@ -219,6 +219,11 @@
 #define LOWPAN_NHC_UDP_CHECKSUMC       0x04
 #define LOWPAN_NHC_UDP_CHECKSUMI       0x00
 
+#define LOWPAN_NHC_UDP_4BIT_PORT       0xF0B0
+#define LOWPAN_NHC_UDP_4BIT_MASK       0xFFF0
+#define LOWPAN_NHC_UDP_8BIT_PORT       0xF000
+#define LOWPAN_NHC_UDP_8BIT_MASK       0xFF00
+
 /* values for port compression, _with checksum_ ie bit 5 set to 0 */
 #define LOWPAN_NHC_UDP_CS_P_00 0xF0 /* all inline */
 #define LOWPAN_NHC_UDP_CS_P_01 0xF1 /* source 16bit inline,
-- 
1.7.2.5


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