Subject: Re: [patch net-next-2.6] net: vlan: make non-hw-accel rx path similar to hw-accel

From: Stephen Hemminger <[email-masked]>
Date: Sat, 2 Apr 2011 08:55:24 -0700

On Sat,  2 Apr 2011 12:26:06 +0200
Jiri Pirko <[email-masked]> wrote:

> Now there are 2 paths for rx vlan frames. When rx-vlan-hw-accel is
> enabled, skb is untagged by NIC, vlan_tci is set and the skb gets into
> vlan code in __netif_receive_skb - vlan_hwaccel_do_receive.
> 
> For non-rx-vlan-hw-accel however, tagged skb goes thru whole
> __netif_receive_skb, it's untagged in ptype_base hander and reinjected
> 
> This incosistency is fixed by this patch. Vlan untagging happens early in
> __netif_receive_skb so the rest of code (ptype_all handlers, rx_handlers)
> see the skb like it was untagged by hw.
> 
> Signed-off-by: Jiri Pirko <[email-masked]>
> ---
>  include/linux/if_vlan.h |   10 ++-
>  net/8021q/vlan.c        |    8 --
>  net/8021q/vlan.h        |    2 -
>  net/8021q/vlan_core.c   |   86 +++++++++++++++++++++++-
>  net/8021q/vlan_dev.c    |  173 -----------------------------------------------
>  net/core/dev.c          |    8 ++-
>  6 files changed, 100 insertions(+), 187 deletions(-)
> 
> diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
> index 635e1fa..998b299 100644
> --- a/include/linux/if_vlan.h
> +++ b/include/linux/if_vlan.h
> @@ -132,7 +132,8 @@ extern u16 vlan_dev_vlan_id(const struct net_device *dev);
>  
>  extern int __vlan_hwaccel_rx(struct sk_buff *skb, struct vlan_group *grp,
>  			     u16 vlan_tci, int polling);
> -extern bool vlan_hwaccel_do_receive(struct sk_buff **skb);
> +extern bool vlan_do_receive(struct sk_buff **skb);
> +extern struct sk_buff *vlan_untag(struct sk_buff *skb);
>  extern gro_result_t
>  vlan_gro_receive(struct napi_struct *napi, struct vlan_group *grp,
>  		 unsigned int vlan_tci, struct sk_buff *skb);
> @@ -166,13 +167,18 @@ static inline int __vlan_hwaccel_rx(struct sk_buff *skb, struct vlan_group *grp,
>  	return NET_XMIT_SUCCESS;
>  }
>  
> -static inline bool vlan_hwaccel_do_receive(struct sk_buff **skb)
> +static inline bool vlan_do_receive(struct sk_buff **skb)
>  {
>  	if ((*skb)->vlan_tci & VLAN_VID_MASK)
>  		(*skb)->pkt_type = PACKET_OTHERHOST;
>  	return false;
>  }

Why the added unnecessary indirection

> +inline struct sk_buff *vlan_untag(struct sk_buff *skb)
> +{
> +	return skb;
> +}

This adds no value.

>  static inline gro_result_t
>  vlan_gro_receive(struct napi_struct *napi, struct vlan_group *grp,
>  		 unsigned int vlan_tci, struct sk_buff *skb)
> diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
> index 7850412..59f0a9d 100644
> --- a/net/8021q/vlan.c
> +++ b/net/8021q/vlan.c
> @@ -49,11 +49,6 @@ const char vlan_version[] = DRV_VERSION;
>  static const char vlan_copyright[] = "Ben Greear <[email-masked]>";
>  static const char vlan_buggyright[] = "David S. Miller <[email-masked]>";
>  
> -static struct packet_type vlan_packet_type __read_mostly = {
> -	.type = cpu_to_be16(ETH_P_8021Q),
> -	.func = vlan_skb_recv, /* VLAN receive method */
> -};
> -
>  /* End of global variables definitions. */
>  
>  static void vlan_group_free(struct vlan_group *grp)
> @@ -688,7 +683,6 @@ static int __init vlan_proto_init(void)
>  	if (err < 0)
>  		goto err4;
>  
> -	dev_add_pack(&vlan_packet_type);
>  	vlan_ioctl_set(vlan_ioctl_handler);
>  	return 0;
>  
> @@ -709,8 +703,6 @@ static void __exit vlan_cleanup_module(void)
>  
>  	unregister_netdevice_notifier(&vlan_notifier_block);
>  
> -	dev_remove_pack(&vlan_packet_type);
> -
>  	unregister_pernet_subsys(&vlan_net_ops);
>  	rcu_barrier(); /* Wait for completion of call_rcu()'s */
>  
> diff --git a/net/8021q/vlan.h b/net/8021q/vlan.h
> index 5687c9b..c3408de 100644
> --- a/net/8021q/vlan.h
> +++ b/net/8021q/vlan.h
> @@ -75,8 +75,6 @@ static inline struct vlan_dev_info *vlan_dev_info(const struct net_device *dev)
>  }
>  
>  /* found in vlan_dev.c */
> -int vlan_skb_recv(struct sk_buff *skb, struct net_device *dev,
> -		  struct packet_type *ptype, struct net_device *orig_dev);
>  void vlan_dev_set_ingress_priority(const struct net_device *dev,
>  				   u32 skb_prio, u16 vlan_prio);
>  int vlan_dev_set_egress_priority(const struct net_device *dev,
> diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
> index ce8e3ab..bc83ecc 100644
> --- a/net/8021q/vlan_core.c
> +++ b/net/8021q/vlan_core.c
> @@ -4,7 +4,7 @@
>  #include <linux/netpoll.h>
>  #include "vlan.h"
>  
> -bool vlan_hwaccel_do_receive(struct sk_buff **skbp)
> +bool vlan_do_receive(struct sk_buff **skbp)
>  {
>  	struct sk_buff *skb = *skbp;
>  	u16 vlan_id = skb->vlan_tci & VLAN_VID_MASK;
> @@ -88,3 +88,87 @@ gro_result_t vlan_gro_frags(struct napi_struct *napi, struct vlan_group *grp,
>  	return napi_gro_frags(napi);
>  }
>  EXPORT_SYMBOL(vlan_gro_frags);
> +
> +static inline struct sk_buff *vlan_check_reorder_header(struct sk_buff *skb)
> +{
> +	if (vlan_dev_info(skb->dev)->flags & VLAN_FLAG_REORDER_HDR) {
> +		if (skb_cow(skb, skb_headroom(skb)) < 0)
> +			skb = NULL;
> +		if (skb) {
> +			/* Lifted from Gleb's VLAN code... */
> +			memmove(skb->data - ETH_HLEN,
> +				skb->data - VLAN_ETH_HLEN, 12);
> +			skb->mac_header += VLAN_HLEN;
> +		}
> +	}
> +	return skb;
> +}

Do not mark code as 'static inline' let compiler decide.

> +static inline void vlan_set_encap_proto(struct sk_buff *skb,
> +					struct vlan_hdr *vhdr)
> +{
> +	__be16 proto;
> +	unsigned char *rawp;
> +
> +	/*
> +	 * Was a VLAN packet, grab the encapsulated protocol, which the layer
> +	 * three protocols care about.
> +	 */
> +
> +	proto = vhdr->h_vlan_encapsulated_proto;
> +	if (ntohs(proto) >= 1536) {
> +		skb->protocol = proto;
> +		return;
> +	}
> +
> +	rawp = skb->data;
> +	if (*(unsigned short *) rawp == 0xFFFF)
> +		/*
> +		 * This is a magic hack to spot IPX packets. Older Novell
> +		 * breaks the protocol design and runs IPX over 802.3 without
> +		 * an 802.2 LLC layer. We look for FFFF which isn't a used
> +		 * 802.2 SSAP/DSAP. This won't work for fault tolerant netware
> +		 * but does for the rest.
> +		 */
> +		skb->protocol = htons(ETH_P_802_3);
> +	else
> +		/*
> +		 * Real 802.2 LLC
> +		 */
> +		skb->protocol = htons(ETH_P_802_2);
> +}

What about doublely tagged packets?

> +struct sk_buff *vlan_untag(struct sk_buff *skb)
> +{
> +	struct vlan_hdr *vhdr;
> +	u16 vlan_tci;
> +
> +	if (unlikely(vlan_tx_tag_present(skb))) {
> +		/* vlan_tci is already set-up so leave this for another time */
> +		return skb;
> +	}
> +
> +	skb = skb_share_check(skb, GFP_ATOMIC);
> +	if (unlikely(!skb))
> +		goto err_free;
> +
> +	if (unlikely(!pskb_may_pull(skb, VLAN_HLEN)))
> +		goto err_free;
> +
> +	vhdr = (struct vlan_hdr *) skb->data;
> +	vlan_tci = ntohs(vhdr->h_vlan_TCI);
> +	__vlan_hwaccel_put_tag(skb, vlan_tci);
> +
> +	skb_pull_rcsum(skb, VLAN_HLEN);
> +	vlan_set_encap_proto(skb, vhdr);
> +
> +	skb = vlan_check_reorder_header(skb);
> +	if (unlikely(!skb))
> +		goto err_free;
> +
> +	return skb;
> +
> +err_free:
> +	kfree_skb(skb);
> +	return NULL;
> +}
> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
> index e34ea9e..b4f061f 100644
> --- a/net/8021q/vlan_dev.c
> +++ b/net/8021q/vlan_dev.c
> @@ -65,179 +65,6 @@ static int vlan_dev_rebuild_header(struct sk_buff *skb)
>  	return 0;
>  }
>  
> -static inline struct sk_buff *vlan_check_reorder_header(struct sk_buff *skb)
> -{
> -	if (vlan_dev_info(skb->dev)->flags & VLAN_FLAG_REORDER_HDR) {
> -		if (skb_cow(skb, skb_headroom(skb)) < 0)
> -			skb = NULL;
> -		if (skb) {
> -			/* Lifted from Gleb's VLAN code... */
> -			memmove(skb->data - ETH_HLEN,
> -				skb->data - VLAN_ETH_HLEN, 12);
> -			skb->mac_header += VLAN_HLEN;
> -		}
> -	}
> -
> -	return skb;
> -}
> -
> -static inline void vlan_set_encap_proto(struct sk_buff *skb,
> -		struct vlan_hdr *vhdr)
> -{
> -	__be16 proto;
> -	unsigned char *rawp;
> -
> -	/*
> -	 * Was a VLAN packet, grab the encapsulated protocol, which the layer
> -	 * three protocols care about.
> -	 */
> -
> -	proto = vhdr->h_vlan_encapsulated_proto;
> -	if (ntohs(proto) >= 1536) {
> -		skb->protocol = proto;
> -		return;
> -	}
> -
> -	rawp = skb->data;
> -	if (*(unsigned short *)rawp == 0xFFFF)
> -		/*
> -		 * This is a magic hack to spot IPX packets. Older Novell
> -		 * breaks the protocol design and runs IPX over 802.3 without
> -		 * an 802.2 LLC layer. We look for FFFF which isn't a used
> -		 * 802.2 SSAP/DSAP. This won't work for fault tolerant netware
> -		 * but does for the rest.
> -		 */
> -		skb->protocol = htons(ETH_P_802_3);
> -	else
> -		/*
> -		 * Real 802.2 LLC
> -		 */
> -		skb->protocol = htons(ETH_P_802_2);
> -}
> -
> -/*
> - *	Determine the packet's protocol ID. The rule here is that we
> - *	assume 802.3 if the type field is short enough to be a length.
> - *	This is normal practice and works for any 'now in use' protocol.
> - *
> - *  Also, at this point we assume that we ARE dealing exclusively with
> - *  VLAN packets, or packets that should be made into VLAN packets based
> - *  on a default VLAN ID.
> - *
> - *  NOTE:  Should be similar to ethernet/eth.c.
> - *
> - *  SANITY NOTE:  This method is called when a packet is moving up the stack
> - *                towards userland.  To get here, it would have already passed
> - *                through the ethernet/eth.c eth_type_trans() method.
> - *  SANITY NOTE 2: We are referencing to the VLAN_HDR frields, which MAY be
> - *                 stored UNALIGNED in the memory.  RISC systems don't like
> - *                 such cases very much...
> - *  SANITY NOTE 2a: According to Dave Miller & Alexey, it will always be
> - *  		    aligned, so there doesn't need to be any of the unaligned
> - *  		    stuff.  It has been commented out now...  --Ben
> - *
> - */
> -int vlan_skb_recv(struct sk_buff *skb, struct net_device *dev,
> -		  struct packet_type *ptype, struct net_device *orig_dev)
> -{
> -	struct vlan_hdr *vhdr;
> -	struct vlan_pcpu_stats *rx_stats;
> -	struct net_device *vlan_dev;
> -	u16 vlan_id;
> -	u16 vlan_tci;
> -
> -	skb = skb_share_check(skb, GFP_ATOMIC);
> -	if (skb == NULL)
> -		goto err_free;
> -
> -	if (unlikely(!pskb_may_pull(skb, VLAN_HLEN)))
> -		goto err_free;
> -
> -	vhdr = (struct vlan_hdr *)skb->data;
> -	vlan_tci = ntohs(vhdr->h_vlan_TCI);
> -	vlan_id = vlan_tci & VLAN_VID_MASK;
> -
> -	rcu_read_lock();
> -	vlan_dev = vlan_find_dev(dev, vlan_id);
> -
> -	/* If the VLAN device is defined, we use it.
> -	 * If not, and the VID is 0, it is a 802.1p packet (not
> -	 * really a VLAN), so we will just netif_rx it later to the
> -	 * original interface, but with the skb->proto set to the
> -	 * wrapped proto: we do nothing here.
> -	 */
> -
> -	if (!vlan_dev) {
> -		if (vlan_id) {
> -			pr_debug("%s: ERROR: No net_device for VID: %u on dev: %s\n",
> -				 __func__, vlan_id, dev->name);
> -			goto err_unlock;
> -		}
> -		rx_stats = NULL;
> -	} else {
> -		skb->dev = vlan_dev;
> -
> -		rx_stats = this_cpu_ptr(vlan_dev_info(skb->dev)->vlan_pcpu_stats);
> -
> -		u64_stats_update_begin(&rx_stats->syncp);
> -		rx_stats->rx_packets++;
> -		rx_stats->rx_bytes += skb->len;
> -
> -		skb->priority = vlan_get_ingress_priority(skb->dev, vlan_tci);
> -
> -		pr_debug("%s: priority: %u for TCI: %hu\n",
> -			 __func__, skb->priority, vlan_tci);
> -
> -		switch (skb->pkt_type) {
> -		case PACKET_BROADCAST:
> -			/* Yeah, stats collect these together.. */
> -			/* stats->broadcast ++; // no such counter :-( */
> -			break;
> -
> -		case PACKET_MULTICAST:
> -			rx_stats->rx_multicast++;
> -			break;
> -
> -		case PACKET_OTHERHOST:
> -			/* Our lower layer thinks this is not local, let's make
> -			 * sure.
> -			 * This allows the VLAN to have a different MAC than the
> -			 * underlying device, and still route correctly.
> -			 */
> -			if (!compare_ether_addr(eth_hdr(skb)->h_dest,
> -						skb->dev->dev_addr))
> -				skb->pkt_type = PACKET_HOST;
> -			break;
> -		default:
> -			break;
> -		}
> -		u64_stats_update_end(&rx_stats->syncp);
> -	}
> -
> -	skb_pull_rcsum(skb, VLAN_HLEN);
> -	vlan_set_encap_proto(skb, vhdr);
> -
> -	if (vlan_dev) {
> -		skb = vlan_check_reorder_header(skb);
> -		if (!skb) {
> -			rx_stats->rx_errors++;
> -			goto err_unlock;
> -		}
> -	}
> -
> -	netif_rx(skb);
> -
> -	rcu_read_unlock();
> -	return NET_RX_SUCCESS;
> -
> -err_unlock:
> -	rcu_read_unlock();
> -err_free:
> -	atomic_long_inc(&dev->rx_dropped);
> -	kfree_skb(skb);
> -	return NET_RX_DROP;
> -}
> -
>  static inline u16
>  vlan_dev_get_egress_qos_mask(struct net_device *dev, struct sk_buff *skb)
>  {
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 3da9fb0..bfe9fce 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -3130,6 +3130,12 @@ another_round:
>  
>  	__this_cpu_inc(softnet_data.processed);
>  
> +	if (skb->protocol == cpu_to_be16(ETH_P_8021Q)) {
> +		skb = vlan_untag(skb);
> +		if (unlikely(!skb))
> +			goto out;
> +	}

This becomes a NOP, why is it here?

>  #ifdef CONFIG_NET_CLS_ACT
>  	if (skb->tc_verd & TC_NCLS) {
>  		skb->tc_verd = CLR_TC_NCLS(skb->tc_verd);
> @@ -3177,7 +3183,7 @@ ncls:
>  			ret = deliver_skb(skb, pt_prev, orig_dev);
>  			pt_prev = NULL;
>  		}
> -		if (vlan_hwaccel_do_receive(&skb)) {
> +		if (vlan_do_receive(&skb)) {
>  			ret = __netif_receive_skb(skb);
>  			goto out;
>  		} else if (unlikely(!skb))

Why rename the function?