Re: [PATCH linux-wpan] 6lowpan: ensure header compression does not corrupt ipv6 header

[Martin Townsend <martin.townsend@xsilon.com>]

Acked-by: Martin Townsend <martin.townsend@xsilon.com>
On 19/09/14 16:42, Simon Vincent wrote:
> Signed-off-by: Simon Vincent <simon.vincent@xsilon.com>
> ---
>   net/ieee802154/6lowpan_rtnl.c | 131 +++++++++++++++++++++++++++++++-----------
>   1 file changed, 97 insertions(+), 35 deletions(-)
>
> diff --git a/net/ieee802154/6lowpan_rtnl.c b/net/ieee802154/6lowpan_rtnl.c
> index 6591d27..cb94504 100644
> --- a/net/ieee802154/6lowpan_rtnl.c
> +++ b/net/ieee802154/6lowpan_rtnl.c
> @@ -71,6 +71,26 @@ struct lowpan_dev_record {
>   	struct list_head list;
>   };
>   
> +union lowpan_addr_u {
> +	/* IPv6 needs big endian here */
> +	__be64 extended;
> +	__be16 short_;
> +};
> +
> +/* don't save pan id, it's intra pan */
> +struct lowpan_addr {
> +	/* non converted address mode bits here
> +	 * make this at first, improve memcmp on this struct
> +	 */
> +	__le16 mode;
> +	union lowpan_addr_u u;
> +};
> +
> +struct lowpan_addr_info {
> +	struct lowpan_addr daddr;
> +	struct lowpan_addr saddr;
> +};
> +
>   static inline struct
>   lowpan_dev_info *lowpan_dev_info(const struct net_device *dev)
>   {
> @@ -85,14 +104,21 @@ static inline void lowpan_address_flip(u8 *src, u8 *dest)
>   		(dest)[IEEE802154_ADDR_LEN - i - 1] = (src)[i];
>   }
>   
> +static inline struct
> +lowpan_addr_info *lowpan_skb_priv(const struct sk_buff *skb)
> +{
> +	WARN_ON_ONCE(skb_headroom(skb) < sizeof(struct lowpan_addr_info));
> +	return (struct lowpan_addr_info *)(skb->data -
> +			sizeof(struct lowpan_addr_info));
> +}
> +
>   static int lowpan_header_create(struct sk_buff *skb, struct net_device *dev,
>   				unsigned short type, const void *_daddr,
>   				const void *_saddr, unsigned int len)
>   {
>   	const u8 *saddr = _saddr;
>   	const u8 *daddr = _daddr;
> -	struct ieee802154_addr sa, da;
> -	struct ieee802154_mac_cb *cb = mac_cb_init(skb);
> +	struct lowpan_addr_info *info;
>   
>   	/* TODO:
>   	 * if this package isn't ipv6 one, where should it be routed?
> @@ -106,41 +132,15 @@ static int lowpan_header_create(struct sk_buff *skb, struct net_device *dev,
>   	raw_dump_inline(__func__, "saddr", (unsigned char *)saddr, 8);
>   	raw_dump_inline(__func__, "daddr", (unsigned char *)daddr, 8);
>   
> -	lowpan_header_compress(skb, dev, type, daddr, saddr, len);
> -
> -	/* NOTE1: I'm still unsure about the fact that compression and WPAN
> -	 * header are created here and not later in the xmit. So wait for
> -	 * an opinion of net maintainers.
> -	 */
> -	/* NOTE2: to be absolutely correct, we must derive PANid information
> -	 * from MAC subif of the 'dev' and 'real_dev' network devices, but
> -	 * this isn't implemented in mainline yet, so currently we assign 0xff
> -	 */
> -	cb->type = IEEE802154_FC_TYPE_DATA;
> -
> -	/* prepare wpan address data */
> -	sa.mode = IEEE802154_ADDR_LONG;
> -	sa.pan_id = ieee802154_mlme_ops(dev)->get_pan_id(dev);
> -	sa.extended_addr = ieee802154_devaddr_from_raw(saddr);
> +	info = lowpan_skb_priv(skb);
>   
> -	/* intra-PAN communications */
> -	da.pan_id = sa.pan_id;
> +	info->daddr.mode = IEEE802154_ADDR_LONG;
> +	memcpy(&info->daddr.u.extended, daddr, sizeof(info->daddr.u.extended));
>   
> -	/* if the destination address is the broadcast address, use the
> -	 * corresponding short address
> -	 */
> -	if (lowpan_is_addr_broadcast(daddr)) {
> -		da.mode = IEEE802154_ADDR_SHORT;
> -		da.short_addr = cpu_to_le16(IEEE802154_ADDR_BROADCAST);
> -	} else {
> -		da.mode = IEEE802154_ADDR_LONG;
> -		da.extended_addr = ieee802154_devaddr_from_raw(daddr);
> -	}
> +	info->saddr.mode = IEEE802154_ADDR_LONG;
> +	memcpy(&info->saddr.u.extended, saddr, sizeof(info->daddr.u.extended));
>   
> -	cb->ackreq = !lowpan_is_addr_broadcast(daddr);
> -
> -	return dev_hard_header(skb, lowpan_dev_info(dev)->real_dev,
> -			type, (void *)&da, (void *)&sa, 0);
> +	return 0;
>   }
>   
>   static int lowpan_give_skb_to_devices(struct sk_buff *skb,
> @@ -338,13 +338,74 @@ err:
>   	return rc;
>   }
>   
> +static int lowpan_header(struct sk_buff *skb, struct net_device *dev)
> +{
> +	struct ieee802154_addr sa, da;
> +	struct ieee802154_mac_cb *cb = mac_cb_init(skb);
> +	struct lowpan_addr_info info;
> +	void *daddr, *saddr;
> +
> +	memcpy(&info, lowpan_skb_priv(skb), sizeof(info));
> +
> +	/* TODO complicated bug why we support extended_addr only */
> +	daddr = &info.daddr.u.extended;
> +	saddr = &info.saddr.u.extended;
> +
> +	lowpan_header_compress(skb, dev, ETH_P_IPV6, daddr, saddr, skb->len);
> +
> +	/* NOTE1: I'm still unsure about the fact that compression and WPAN
> +	 * header are created here and not later in the xmit. So wait for
> +	 * an opinion of net maintainers.
> +	 */
> +	/* NOTE2: to be absolutely correct, we must derive PANid information
> +	 * from MAC subif of the 'ldev' and 'wdev' network devices, but
> +	 * this isn't implemented in mainline yet, so currently we assign 0xff
> +	 */
> +	cb->type = IEEE802154_FC_TYPE_DATA;
> +
> +	/* prepare wpan address data */
> +	sa.mode = IEEE802154_ADDR_LONG;
> +	sa.pan_id = ieee802154_mlme_ops(dev)->get_pan_id(dev);
> +	sa.extended_addr = ieee802154_devaddr_from_raw(saddr);
> +
> +	/* intra-PAN communications */
> +	da.pan_id = sa.pan_id;
> +
> +	/* if the destination address is the broadcast address, use the
> +	 * corresponding short address
> +	 */
> +	if (lowpan_is_addr_broadcast((const u8 *)daddr)) {
> +		da.mode = IEEE802154_ADDR_SHORT;
> +		da.short_addr = cpu_to_le16(IEEE802154_ADDR_BROADCAST);
> +		cb->ackreq = false;
> +	} else {
> +		da.mode = IEEE802154_ADDR_LONG;
> +		da.extended_addr = ieee802154_devaddr_from_raw(daddr);
> +		cb->ackreq = true;
> +	}
> +
> +	return dev_hard_header(skb, lowpan_dev_info(dev)->real_dev,
> +			ETH_P_IPV6, (void *)&da, (void *)&sa, 0);
> +}
> +
>   static netdev_tx_t lowpan_xmit(struct sk_buff *skb, struct net_device *dev)
>   {
>   	struct ieee802154_hdr wpan_hdr;
> -	int max_single;
> +	int max_single, ret;
>   
>   	pr_debug("package xmit\n");
>   
> +	/* We must take a copy of the skb before we modify/replace the ipv6
> +	 * header as the header could be used elsewhere
> +	 */
> +	skb = skb_unshare(skb, GFP_KERNEL);
> +
> +	ret = lowpan_header(skb, dev);
> +	if (ret < 0) {
> +		kfree_skb(skb);
> +		return NET_XMIT_DROP;
> +	}
> +
>   	if (ieee802154_hdr_peek(skb, &wpan_hdr) < 0) {
>   		kfree_skb(skb);
>   		return NET_XMIT_DROP;