Re: [PATCHv5 bluetooth-next 1/3] 6lowpan: add generic nhc layer interface

[Stefan Schmidt <s.schmidt@samsung.com>]

Hello.

On 09/01/15 16:42, Alexander Aring wrote:
> 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@gmail.com>
> Cc: Jukka Rissanen <jukka.rissanen@linux.intel.com>
> Cc: Martin Townsend <mtownsend1973@gmail.com>
> ---
>   net/6lowpan/Makefile |   2 +-
>   net/6lowpan/nhc.c    | 241
> +++++++++++++++++++++++++++++++++++++++++++++++++++
>   net/6lowpan/nhc.h    | 146 +++++++++++++++++++++++++++++++
>   3 files changed, 388 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..4215602 100644
> --- a/net/6lowpan/Makefile
> +++ b/net/6lowpan/Makefile
> @@ -1,3 +1,3 @@
>   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..3c0dc77b0
> --- /dev/null
> +++ b/net/6lowpan/nhc.c
> @@ -0,0 +1,241 @@
> +/*
> + *	6LoWPAN next header compression
> + *
> + *
> + *	Authors:
> + *	Alexander Aring		<aar@pengutronix.de>
> + *
> + *	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 DEFINE_SPINLOCK(lowpan_nhc_lock);
> +
> +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);
> +}
> +
> +static 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;
> +}
> +
> +int lowpan_nhc_check_compression(struct sk_buff *skb,
> +				 const struct ipv6hdr *hdr, u8 **hc_ptr,
> +				 u8 *iphc0)
> +{
> +	struct lowpan_nhc *nhc;
> +
> +	spin_lock_bh(&lowpan_nhc_lock);
> +
> +	nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
> +	if (nhc && nhc->compress)
> +		*iphc0 |= LOWPAN_IPHC_NH_C;
> +	else
> +		lowpan_push_hc_data(hc_ptr, &hdr->nexthdr,
> +				    sizeof(hdr->nexthdr));
> +
> +	spin_unlock_bh(&lowpan_nhc_lock);
> +
> +	return 0;
> +}
> +
> +int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr
> *hdr,
> +			      u8 **hc_ptr)
> +{
> +	int ret;
> +	struct lowpan_nhc *nhc;
> +
> +	spin_lock_bh(&lowpan_nhc_lock);
> +
> +	nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
> +	/* check if the nhc module was removed in unlocked part.
> +	 * TODO: this is a workaround we should prevent unloading
> +	 * of nhc modules while unlocked part, this will always drop
> +	 * the lowpan packet but it's very unlikely.
> +	 *
> +	 * Solution isn't easy because we need to decide at
> +	 * lowpan_nhc_check_compression if we do a compression or not.
> +	 * Because the inline data which is added to skb, we can't move
> this
> +	 * handling.
> +	 */
> +	if (unlikely(!nhc || !nhc->compress)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	/* In the case of RAW sockets the transport header is not set by
> +	 * the ip6 stack so we must set it ourselves
> +	 */
> +	if (skb->transport_header == skb->network_header)
> +		skb_set_transport_header(skb, sizeof(struct ipv6hdr));
> +
> +	ret = nhc->compress(skb, hc_ptr);
> +	if (ret < 0)
> +		goto out;
> +
> +	/* skip the transport header */
> +	skb_pull(skb, nhc->nexthdrlen);
> +
> +out:
> +	spin_unlock_bh(&lowpan_nhc_lock);
> +
> +	return ret;
> +}
> +
> +int lowpan_nhc_do_uncompression(struct sk_buff *skb, struct net_device
> *dev,
> +				struct ipv6hdr *hdr)
> +{
> +	struct lowpan_nhc *nhc;
> +	int ret;
> +
> +	spin_lock_bh(&lowpan_nhc_lock);
> +
> +	nhc = lowpan_nhc_by_nhcid(skb);
> +	if (nhc) {
> +		if (nhc->uncompress) {
> +			ret = nhc->uncompress(skb, sizeof(struct ipv6hdr)
> +
> +					      nhc->nexthdrlen);
> +			if (ret < 0) {
> +				spin_unlock_bh(&lowpan_nhc_lock);
> +				return ret;
> +			}
> +		} else {
> +			spin_unlock_bh(&lowpan_nhc_lock);
> +			netdev_warn(dev, "received nhc id for %s which is
> not implemented.\n",
> +				    nhc->name);
> +			return -ENOTSUPP;
> +		}
> +	} else {
> +		spin_unlock_bh(&lowpan_nhc_lock);
> +		netdev_warn(dev, "received unknown nhc id which was not
> found.\n");
> +		return -ENOENT;
> +	}
> +
> +	hdr->nexthdr = nhc->nexthdr;
> +	skb_reset_transport_header(skb);
> +	raw_dump_table(__func__, "raw transport header dump",
> +		       skb_transport_header(skb), nhc->nexthdrlen);
> +
> +	spin_unlock_bh(&lowpan_nhc_lock);
> +
> +	return 0;
> +}
> +
> +int lowpan_nhc_add(struct lowpan_nhc *nhc)
> +{
> +	int ret;
> +
> +	if (!nhc->idlen || !nhc->idsetup)
> +		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);
> +
> +	spin_lock_bh(&lowpan_nhc_lock);
> +
> +	if (lowpan_nexthdr_nhcs[nhc->nexthdr]) {
> +		ret = -EEXIST;
> +		goto out;
> +	}
> +
> +	ret = lowpan_nhc_insert(nhc);
> +	if (ret < 0)
> +		goto out;
> +
> +	lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
> +out:
> +	spin_unlock_bh(&lowpan_nhc_lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL(lowpan_nhc_add);
> +
> +void lowpan_nhc_del(struct lowpan_nhc *nhc)
> +{
> +	spin_lock_bh(&lowpan_nhc_lock);
> +
> +	lowpan_nhc_remove(nhc);
> +	lowpan_nexthdr_nhcs[nhc->nexthdr] = NULL;
> +
> +	spin_unlock_bh(&lowpan_nhc_lock);
> +
> +	synchronize_net();
> +}
> +EXPORT_SYMBOL(lowpan_nhc_del);
> diff --git a/net/6lowpan/nhc.h b/net/6lowpan/nhc.h
> new file mode 100644
> index 0000000..ed44938
> --- /dev/null
> +++ b/net/6lowpan/nhc.h
> @@ -0,0 +1,146 @@
> +#ifndef __6LOWPAN_NHC_H
> +#define __6LOWPAN_NHC_H
> +
> +#include <linux/skbuff.h>
> +#include <linux/rbtree.h>
> +#include <linux/module.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,	\
> +		   _hdrlen, _idsetup, _idlen,	\
> +		   _uncompress, _compress)	\
> +static u8 __nhc##_val[_idlen];			\
> +static u8 __nhc##_mask[_idlen];			\
> +static struct lowpan_nhc __nhc = {		\
> +	.name		= _name,		\
> +	.nexthdr	= _nexthdr,		\
> +	.nexthdrlen	= _hdrlen,		\
> +	.id		= __nhc##_val,		\
> +	.idmask		= __nhc##_mask,		\
> +	.idlen		= _idlen,		\
> +	.idsetup	= _idsetup,		\
> +	.uncompress	= _uncompress,		\
> +	.compress	= _compress,		\
> +}
> +
> +#define module_lowpan_nhc(__nhc)		\
> +static int __init __nhc##_init(void)		\
> +{						\
> +	return lowpan_nhc_add(&(__nhc));	\
> +}						\
> +module_init(__nhc##_init);			\
> +static void __exit __nhc##_exit(void)		\
> +{						\
> +	lowpan_nhc_del(&(__nhc));		\
> +}						\
> +module_exit(__nhc##_exit);
> +
> +/**
> + * struct lowpan_nhc - hold 6lowpan next hdr compression ifnformation
> + *
> + * @node: holder for the rbtree.
> + * @name: name of the specific next header compression
> + * @nexthdr: next header value of the protocol which should be
> compressed.
> + * @nexthdrlen: ipv6 nexthdr len for the reserved space.
> + * @id: array for nhc id. Note this need to be in network byteorder.
> + * @mask: array for nhc id mask. Note this need to be in network
> byteorder.
> + * @len: the length of the next header id and mask.
> + * @setup: callback to setup fill the next header id value and mask.
> + * @compress: callback to do the header compression.
> + * @uncompress: callback to do the header uncompression.
> + */
> +struct lowpan_nhc {
> +	struct rb_node	node;
> +	const char	*name;
> +	const u8	nexthdr;
> +	const size_t	nexthdrlen;
> +	u8		*id;
> +	u8		*idmask;
> +	const size_t	idlen;
> +
> +	void		(*idsetup)(struct lowpan_nhc *nhc);
> +	int		(*uncompress)(struct sk_buff *skb, size_t needed);
> +	int		(*compress)(struct sk_buff *skb, u8 **hc_ptr);
> +};
> +
> +/**
> + * lowpan_nhc_by_nexthdr - return the 6lowpan nhc by ipv6 nexthdr.
> + *
> + * @nexthdr: ipv6 nexthdr value.
> + */
> +struct lowpan_nhc *lowpan_nhc_by_nexthdr(u8 nexthdr);
> +
> +/**
> + * lowpan_nhc_check_compression - checks if we support compression
> format. If
> + *	we support the nhc by nexthdr field, the 6LoWPAN iphc NHC bit will
> be
> + *	set. If we don't support nexthdr will be added as inline data to
> the
> + *	6LoWPAN header.
> + *
> + * @skb: skb of 6LoWPAN header to read nhc and replace header.
> + * @hdr: ipv6hdr to check the nexthdr value
> + * @hc_ptr: pointer for 6LoWPAN header which should increment at the end
> of
> + *	    replaced header.
> + * @iphc0: iphc0 pointer to set the 6LoWPAN NHC bit
> + */
> +int lowpan_nhc_check_compression(struct sk_buff *skb,
> +				 const struct ipv6hdr *hdr, u8 **hc_ptr,
> +				 u8 *iphc0);
> +
> +/**
> + * lowpan_nhc_do_compression - calling compress callback for nhc
> + *
> + * @skb: skb of 6LoWPAN header to read nhc and replace header.
> + * @hdr: ipv6hdr to set the nexthdr value
> + * @hc_ptr: pointer for 6LoWPAN header which should increment at the end
> of
> + *	    replaced header.
> + */
> +int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr
> *hdr,
> +			      u8 **hc_ptr);
> +
> +/**
> + * lowpan_nhc_do_uncompression - calling uncompress callback for nhc
> + *
> + * @nhc: 6LoWPAN nhc context, get by lowpan_nhc_by_ functions.
> + * @skb: skb of 6LoWPAN header, skb->data should be pointed to nhc id
> value.
> + * @dev: netdevice for print logging information.
> + * @hdr: ipv6hdr for setting nexthdr value.
> + */
> +int lowpan_nhc_do_uncompression(struct sk_buff *skb, struct net_device
> *dev,
> +				struct ipv6hdr *hdr);
> +
> +/**
> + * lowpan_nhc_add - register a next header compression to framework
> + *
> + * @nhc: nhc which should be add.
> + */
> +int lowpan_nhc_add(struct lowpan_nhc *nhc);
> +
> +/**
> + * lowpan_nhc_del - delete a next header compression from framework
> + *
> + * @nhc: nhc which should be delete.
> + */
> +void lowpan_nhc_del(struct lowpan_nhc *nhc);
> +
> +/**
> + * lowpan_nhc_init - adding all default nhcs
> + */
> +void lowpan_nhc_init(void);
> +
> +#endif /* __6LOWPAN_NHC_H */
>

Reviewed-by: Stefan Schmidt <s.schmidt@samsung.com>

regards
Stefan Schmidt