Re: [PATCH 4/6] [6LoWPAN] UDP header compression

[Dmitry Eremin-Solenikov <dbaryshkov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 11/2/11, Alexander Smirnov <alex.bluesman.smirnov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> This patch adds support for UDP header compression.
> Derived from Contiki OS.

>From my point of view, this code would also benefit from being refactored
to a separate function.

>
> Signed-off-by: Alexander Smirnov <alex.bluesman.smirnov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  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
>
>


-- 
With best wishes
Dmitry

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