Hi Alex,
> This patch adds a generic next header compression layer interface. There
> exists various methods to do a header compression after 6LoWPAN header
> to save payload. This introduce a generic nhc header which allow a
> simple adding of a new header compression format instead of a static
> implementation inside the 6LoWPAN header compression and uncompression
> function.
>
> Signed-off-by: Alexander Aring <alex.aring@xxxxxxxxx>
> Cc: Jukka Rissanen <jukka.rissanen@xxxxxxxxxxxxxxx>
> Cc: Martin Townsend <mtownsend1973@xxxxxxxxx>
> ---
> net/6lowpan/Makefile | 4 +-
> net/6lowpan/nhc.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++++++
> net/6lowpan/nhc.h | 128 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 313 insertions(+), 1 deletion(-)
> create mode 100644 net/6lowpan/nhc.c
> create mode 100644 net/6lowpan/nhc.h
>
> diff --git a/net/6lowpan/Makefile b/net/6lowpan/Makefile
> index 415886b..ba6bf47 100644
> --- a/net/6lowpan/Makefile
> +++ b/net/6lowpan/Makefile
> @@ -1,3 +1,5 @@
> obj-$(CONFIG_6LOWPAN) := 6lowpan.o
>
> -6lowpan-y := iphc.o
> +6lowpan-y := \
> + iphc.o \
> + nhc.o
> diff --git a/net/6lowpan/nhc.c b/net/6lowpan/nhc.c
> new file mode 100644
> index 0000000..e0b2bd1
> --- /dev/null
> +++ b/net/6lowpan/nhc.c
> @@ -0,0 +1,182 @@
> +/*
> + * 6LoWPAN next header compression
> + *
> + *
> + * Authors:
> + * Alexander Aring <aar@xxxxxxxxxxxxxx>
> + *
> + * 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 <linux/netdevice.h>
> +
> +#include <net/ipv6.h>
> +
> +#include "nhc.h"
> +
> +static struct rb_root rb_root = RB_ROOT;
> +static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX];
> +
> +static int lowpan_nhc_insert(struct lowpan_nhc *nhc)
> +{
> + struct rb_node **new = &rb_root.rb_node, *parent = NULL;
> +
> + /* Figure out where to put new node */
> + while (*new) {
> + struct lowpan_nhc *this = container_of(*new, struct lowpan_nhc,
> + node);
> + int result, len_dif, len;
> +
> + len_dif = nhc->idlen - this->idlen;
> +
> + if (nhc->idlen < this->idlen)
> + len = nhc->idlen;
> + else
> + len = this->idlen;
> +
> + result = memcmp(nhc->id, this->id, len);
> + if (!result)
> + result = len_dif;
> +
> + parent = *new;
> + if (result < 0)
> + new = &((*new)->rb_left);
> + else if (result > 0)
> + new = &((*new)->rb_right);
> + else
> + return -EEXIST;
> + }
> +
> + /* Add new node and rebalance tree. */
> + rb_link_node(&nhc->node, parent, new);
> + rb_insert_color(&nhc->node, &rb_root);
> +
> + return 0;
> +}
> +
> +static void lowpan_nhc_remove(struct lowpan_nhc *nhc)
> +{
> + rb_erase(&nhc->node, &rb_root);
> +}
> +
> +struct lowpan_nhc *lowpan_nhc_by_nhcid(const struct sk_buff *skb)
> +{
> + struct rb_node *node = rb_root.rb_node;
> + const u8 *nhcid_skb_ptr = skb->data;
> +
> + while (node) {
> + struct lowpan_nhc *nhc = container_of(node, struct lowpan_nhc,
> + node);
> + u8 nhcid_skb_ptr_masked[LOWPAN_NHC_MAX_ID_LEN];
> + int result, i;
> +
> + if (nhcid_skb_ptr + nhc->idlen > skb->data + skb->len)
> + return NULL;
> +
> + /* copy and mask afterwards the nhid value from skb */
> + memcpy(nhcid_skb_ptr_masked, nhcid_skb_ptr, nhc->idlen);
> + for (i = 0; i < nhc->idlen; i++)
> + nhcid_skb_ptr_masked[i] &= nhc->idmask[i];
> +
> + result = memcmp(nhcid_skb_ptr_masked, nhc->id, nhc->idlen);
> + if (result < 0)
> + node = node->rb_left;
> + else if (result > 0)
> + node = node->rb_right;
> + else
> + return nhc;
> + }
> +
> + return NULL;
> +}
> +
> +struct lowpan_nhc *lowpan_nhc_by_nexthdr(u8 nexthdr)
> +{
> + return lowpan_nexthdr_nhcs[nexthdr];
> +}
> +
> +int lowpan_nhc_do_compression(struct lowpan_nhc *nhc, struct sk_buff *skb,
> + u8 **hc_ptr, u8 *iphc0)
> +{
> + int ret;
> +
> + if (!nhc)
> + return 0;
> +
> + ret = nhc->compress(skb, hc_ptr);
> + if (ret == 0)
> + *iphc0 |= LOWPAN_IPHC_NH_C;
> +
> + return ret;
> +}
> +
> +int lowpan_nhc_do_uncompression(struct sk_buff *skb, struct ipv6hdr *hdr)
> +{
> + struct lowpan_nhc *nhc;
> + /* default dropping if nothing found */
> + int ret = -ENOTSUPP;
> +
> + nhc = lowpan_nhc_by_nhcid(skb);
> + if (nhc) {
> + ret = nhc->uncompress(skb, sizeof(*hdr) + nhc->nexthdrlen);
> + if (ret == 0) {
> + hdr->nexthdr = nhc->nexthdr;
> + skb_reset_transport_header(skb);
> + raw_dump_table(__func__, "raw transport header dump",
> + skb_transport_header(skb),
> + nhc->nexthdrlen);
> + } else if (ret == -ENOTSUPP) {
> + netdev_warn(skb->dev, "received %s which is not supported for uncompression.\n",
> + nhc->name);
> + }
> + } else {
> + netdev_warn(skb->dev, "received nhc which is not supported. Dropping.\n");
> + }
> +
> + return ret;
> +}
> +
> +int lowpan_nhc_add(struct lowpan_nhc *nhc)
> +{
> + int ret;
> +
> + if (!nhc->idlen || !nhc->idsetup || !nhc->compress || !nhc->uncompress)
> + return -EINVAL;
> +
> + WARN_ONCE(nhc->idlen > LOWPAN_NHC_MAX_ID_LEN,
> + "LOWPAN_NHC_MAX_ID_LEN should be updated to %d.\n",
> + nhc->idlen);
> +
> + nhc->idsetup(nhc);
> +
> + if (lowpan_nexthdr_nhcs[nhc->nexthdr])
> + return -EEXIST;
> +
> + ret = lowpan_nhc_insert(nhc);
> + if (ret < 0)
> + goto out;
> +
> + lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
> +out:
> + return ret;
> +}
> +
> +void lowpan_nhc_del(struct lowpan_nhc *nhc)
> +{
> + lowpan_nhc_remove(nhc);
> + lowpan_nexthdr_nhcs[nhc->nexthdr] = NULL;
> +
> + synchronize_net();
> +}
> +
> +int lowpan_nhc_init(void)
> +{
> + return 0;
> +}
> +
> +void lowpan_nhc_cleanup(void)
> +{
> +}
> diff --git a/net/6lowpan/nhc.h b/net/6lowpan/nhc.h
> new file mode 100644
> index 0000000..f83f06e
> --- /dev/null
> +++ b/net/6lowpan/nhc.h
> @@ -0,0 +1,128 @@
> +#ifndef __6LOWPAN_NHC_H
> +#define __6LOWPAN_NHC_H
> +
> +#include <linux/skbuff.h>
> +#include <linux/rbtree.h>
> +
> +#include <net/6lowpan.h>
> +#include <net/ipv6.h>
> +
> +#define LOWPAN_NHC_MAX_ID_LEN 1
> +
> +/**
> + * LOWPAN_NHC - helper macro to generate nh id fields and lowpan_nhc struct
> + *
> + * @__nhc: variable name of the lowpan_nhc struct.
> + * @_name: const char * of common header compression name.
> + * @_nexthdr: ipv6 nexthdr field for the header compression.
> + * @_nexthdrlen: ipv6 nexthdr len for the reserved space.
> + * @_idsetup: callback to setup id and mask values.
> + * @_idlen: len for the next header id and mask, should be always the same.
> + * @_uncompress: callback for uncompression call.
> + * @_compress: callback for compression call.
> + */
> +#define LOWPAN_NHC(__nhc, _name, _nexthdr, \
> + _nexthdrlen, _idsetup, \
> + _idlen, _uncompress, \
> + _compress) \
> + static u8 __nhc##_val[_idlen]; \
> + static u8 __nhc##_mask[_idlen]; \
> + static struct lowpan_nhc __nhc = { \
any reason why these are not declared as static const?
> + .name = _name, \
> + .nexthdr = _nexthdr, \
> + .nexthdrlen = _nexthdrlen, \
> + .id = __nhc##_val, \
> + .idmask = __nhc##_mask, \
> + .idlen = _idlen, \
> + .idsetup = _idsetup, \
> + .uncompress = _uncompress, \
> + .compress = _compress, \
> + }
I also wonder if we should mix lowpan_nhc_add and lowpan_nhc_del handling into this macro as well. If the next header compression would be auto-loadable modules, then creating a module_lowpan_nhc() macro similar to module_usb_driver() etc. would help. We could in theory use module aliases to auto-load compression modules once needed. However it might be a bit too much overhead.
Regards
Marcel
--
To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
