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6LoWPAN: UDP header compression
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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>
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alex.bluesman.smirnov@gmail.com authored and David S. Miller committed Nov 14, 2011
1 parent 4d039f6 commit 3bd5b95
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Showing 2 changed files with 52 additions and 4 deletions.
51 changes: 47 additions & 4 deletions net/ieee802154/6lowpan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down
5 changes: 5 additions & 0 deletions net/ieee802154/6lowpan.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand Down

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