Commit d32aebfd authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'gso_forward' 



Florian Westphal says:

====================
net: ip: push gso skb forwarding handling down the stack

Turns out doing the segmentation in forwarding was not a bright idea,
there are corner-cases where this has unintended side-effects.

This patch pushes the segmentation downwards.

After this, netif_skb_dev_features() function can be removed
again, it was only added to fetch the features of the output device,
we can just use skb->dev after the pushdown.

Tested with following setup:

host -> kvm_router  -> kvm_host
  mtu 1500        mtu1280

- 'host' has route to kvm_host with locked mtu of 1500
- gso/gro enabled on all interfaces

Did tests with all of following combinations:
- netfilter conntrack off and on on kvm_router
- virtio-net and e1000 driver on kvm_router
- tcp and udp bulk xmit from host to kvm_host

for tcp, I added TCPMSS mangling on kvm_host to make it lie about tcp mss.

Also added a dummy '-t mangle -A POSTROUTING -p udp -f'
rule to make sure no udp fragments are seen in the 'conntrack on'
and 'virtio-net' case.

Also checked (with ping -M do -s 1400)' that it still sends the wanted
icmp error message when size exceeds 1280.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 418a3156 c1e756bf

include/linux/netdevice.h

+1 −6
Original line number Diff line number Diff line
@@ -3180,12 +3180,7 @@ void netdev_change_features(struct net_device *dev); 
void netif_stacked_transfer_operstate(const struct net_device *rootdev,

					struct net_device *dev);



netdev_features_t netif_skb_dev_features(struct sk_buff *skb,

					 const struct net_device *dev);

static inline netdev_features_t netif_skb_features(struct sk_buff *skb)

{

	return netif_skb_dev_features(skb, skb->dev);

}

netdev_features_t netif_skb_features(struct sk_buff *skb);



static inline bool net_gso_ok(netdev_features_t features, int gso_type)

{

net/core/dev.c

+10 −12
Original line number Diff line number Diff line
@@ -2418,7 +2418,7 @@ EXPORT_SYMBOL(netdev_rx_csum_fault); 
 * 2. No high memory really exists on this machine.

 */



static int illegal_highdma(const struct net_device *dev, struct sk_buff *skb)

static int illegal_highdma(struct net_device *dev, struct sk_buff *skb)

{

#ifdef CONFIG_HIGHMEM

	int i;
@@ -2493,7 +2493,6 @@ static int dev_gso_segment(struct sk_buff *skb, netdev_features_t features) 
}



static netdev_features_t harmonize_features(struct sk_buff *skb,

					    const struct net_device *dev,

	netdev_features_t features)

{

	int tmp;
@@ -2501,30 +2500,29 @@ static netdev_features_t harmonize_features(struct sk_buff *skb, 
	if (skb->ip_summed != CHECKSUM_NONE &&

	    !can_checksum_protocol(features, skb_network_protocol(skb, &tmp))) {

		features &= ~NETIF_F_ALL_CSUM;

	} else if (illegal_highdma(dev, skb)) {

	} else if (illegal_highdma(skb->dev, skb)) {

		features &= ~NETIF_F_SG;

	}



	return features;

}



netdev_features_t netif_skb_dev_features(struct sk_buff *skb,

					 const struct net_device *dev)

netdev_features_t netif_skb_features(struct sk_buff *skb)

{

	__be16 protocol = skb->protocol;

	netdev_features_t features = dev->features;

	netdev_features_t features = skb->dev->features;



	if (skb_shinfo(skb)->gso_segs > dev->gso_max_segs)

	if (skb_shinfo(skb)->gso_segs > skb->dev->gso_max_segs)

		features &= ~NETIF_F_GSO_MASK;



	if (protocol == htons(ETH_P_8021Q) || protocol == htons(ETH_P_8021AD)) {

		struct vlan_ethhdr *veh = (struct vlan_ethhdr *)skb->data;

		protocol = veh->h_vlan_encapsulated_proto;

	} else if (!vlan_tx_tag_present(skb)) {

		return harmonize_features(skb, dev, features);

		return harmonize_features(skb, features);

	}



	features &= (dev->vlan_features | NETIF_F_HW_VLAN_CTAG_TX |

	features &= (skb->dev->vlan_features | NETIF_F_HW_VLAN_CTAG_TX |

					       NETIF_F_HW_VLAN_STAG_TX);



	if (protocol == htons(ETH_P_8021Q) || protocol == htons(ETH_P_8021AD))
@@ -2532,9 +2530,9 @@ netdev_features_t netif_skb_dev_features(struct sk_buff *skb, 
				NETIF_F_GEN_CSUM | NETIF_F_HW_VLAN_CTAG_TX |

				NETIF_F_HW_VLAN_STAG_TX;



	return harmonize_features(skb, dev, features);

	return harmonize_features(skb, features);

}

EXPORT_SYMBOL(netif_skb_dev_features);

EXPORT_SYMBOL(netif_skb_features);



int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,

			struct netdev_queue *txq)

net/ipv4/ip_forward.c

+0 −50
Original line number Diff line number Diff line
@@ -56,53 +56,6 @@ static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu) 
	return true;

}



static bool ip_gso_exceeds_dst_mtu(const struct sk_buff *skb)

{

	unsigned int mtu;



	if (skb->local_df || !skb_is_gso(skb))

		return false;



	mtu = ip_dst_mtu_maybe_forward(skb_dst(skb), true);



	/* if seglen > mtu, do software segmentation for IP fragmentation on

	 * output.  DF bit cannot be set since ip_forward would have sent

	 * icmp error.

	 */

	return skb_gso_network_seglen(skb) > mtu;

}



/* called if GSO skb needs to be fragmented on forward */

static int ip_forward_finish_gso(struct sk_buff *skb)

{

	struct dst_entry *dst = skb_dst(skb);

	netdev_features_t features;

	struct sk_buff *segs;

	int ret = 0;



	features = netif_skb_dev_features(skb, dst->dev);

	segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);

	if (IS_ERR(segs)) {

		kfree_skb(skb);

		return -ENOMEM;

	}



	consume_skb(skb);



	do {

		struct sk_buff *nskb = segs->next;

		int err;



		segs->next = NULL;

		err = dst_output(segs);



		if (err && ret == 0)

			ret = err;

		segs = nskb;

	} while (segs);



	return ret;

}



static int ip_forward_finish(struct sk_buff *skb)

{
@@ -114,9 +67,6 @@ static int ip_forward_finish(struct sk_buff *skb) 
	if (unlikely(opt->optlen))

		ip_forward_options(skb);



	if (ip_gso_exceeds_dst_mtu(skb))

		return ip_forward_finish_gso(skb);



	return dst_output(skb);

}

net/ipv4/ip_output.c

+48 −3
Original line number Diff line number Diff line
@@ -211,6 +211,48 @@ static inline int ip_finish_output2(struct sk_buff *skb) 
	return -EINVAL;

}



static int ip_finish_output_gso(struct sk_buff *skb)

{

	netdev_features_t features;

	struct sk_buff *segs;

	int ret = 0;



	/* common case: locally created skb or seglen is <= mtu */

	if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||

	      skb_gso_network_seglen(skb) <= ip_skb_dst_mtu(skb))

		return ip_finish_output2(skb);



	/* Slowpath -  GSO segment length is exceeding the dst MTU.

	 *

	 * This can happen in two cases:

	 * 1) TCP GRO packet, DF bit not set

	 * 2) skb arrived via virtio-net, we thus get TSO/GSO skbs directly

	 * from host network stack.

	 */

	features = netif_skb_features(skb);

	segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);

	if (IS_ERR(segs)) {

		kfree_skb(skb);

		return -ENOMEM;

	}



	consume_skb(skb);



	do {

		struct sk_buff *nskb = segs->next;

		int err;



		segs->next = NULL;

		err = ip_fragment(segs, ip_finish_output2);



		if (err && ret == 0)

			ret = err;

		segs = nskb;

	} while (segs);



	return ret;

}



static int ip_finish_output(struct sk_buff *skb)

{

#if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
@@ -220,9 +262,12 @@ static int ip_finish_output(struct sk_buff *skb) 
		return dst_output(skb);

	}

#endif

	if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))

	if (skb_is_gso(skb))

		return ip_finish_output_gso(skb);



	if (skb->len > ip_skb_dst_mtu(skb))

		return ip_fragment(skb, ip_finish_output2);

	else



	return ip_finish_output2(skb);

}

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