vxlan: keep original skb ownership (8f646c92) · Commits · 戴 / test

Sathya Perla posted a patch trying to address following problem : <quote> The vxlan driver sets itself as the socket owner for all the TX flows it encapsulates (using vxlan_set_owner()) and assigns it's own skb destructor. This causes all tunneled traffic to land up on only one TXQ as all encapsulated skbs refer to the vxlan socket and not the original socket. Also, the vxlan skb destructor breaks some functionality for tunneled traffic like wmem accounting and as TCP small queues and FQ/pacing packet scheduler. </quote> I reworked Sathya patch and added some explanations. vxlan_xmit() can avoid one skb_clone()/dev_kfree_skb() pair and gain better drop monitor accuracy, by calling kfree_skb() when appropriate. The UDP socket used by vxlan to perform encapsulation of xmit packets do not need to be alive while packets leave vxlan code. Its better to keep original socket ownership to get proper feedback from qdisc and NIC layers. We use skb->sk to A) control amount of bytes/packets queued on behalf of a socket, but prior vxlan code did the skb->sk transfert without any limit/control on vxlan socket sk_sndbuf. B) security purposes (as selinux) or netfilter uses, and I do not think anything is prepared to handle vxlan stacked case in this area. By not changing ownership, vxlan tunnels behave like other tunnels. As Stephen mentioned, we might do the same change in L2TP. Reported-by:

Sathya Perla <sathya.perla@emulex.com> Signed-off-by:

Eric Dumazet <edumazet@google.com> Cc: Stephen Hemminger <stephen@networkplumber.org> Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

+10 −21

Original line number	Diff line number	Diff line
		@@ -1381,20 +1381,6 @@ static bool route_shortcircuit(struct net_device dev, struct sk_buff skb)
		return false;
		}

		static void vxlan_sock_put(struct sk_buff *skb)
		{
		sock_put(skb->sk);
		}

		/* On transmit, associate with the tunnel socket */
		static void vxlan_set_owner(struct sock sk, struct sk_buff skb)
		{
		skb_orphan(skb);
		sock_hold(sk);
		skb->sk = sk;
		skb->destructor = vxlan_sock_put;
		}

		/* Compute source port for outgoing packet
		* first choice to use L4 flow hash since it will spread
		* better and maybe available from hardware
		@@ -1514,8 +1500,6 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,
		ip6h->daddr = *daddr;
		ip6h->saddr = *saddr;

		vxlan_set_owner(vs->sock->sk, skb);

		err = handle_offloads(skb);
		if (err)
		return err;
		@@ -1572,8 +1556,6 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,
		uh->len = htons(skb->len);
		uh->check = 0;

		vxlan_set_owner(vs->sock->sk, skb);

		err = handle_offloads(skb);
		if (err)
		return err;
		@@ -1786,7 +1768,7 @@ static netdev_tx_t vxlan_xmit(struct sk_buff skb, struct net_device dev)
		struct vxlan_dev *vxlan = netdev_priv(dev);
		struct ethhdr *eth;
		bool did_rsc = false;
		struct vxlan_rdst *rdst;
		struct vxlan_rdst rdst, fdst = NULL;
		struct vxlan_fdb *f;

		skb_reset_mac_header(skb);
		@@ -1828,7 +1810,7 @@ static netdev_tx_t vxlan_xmit(struct sk_buff skb, struct net_device dev)
		vxlan_fdb_miss(vxlan, eth->h_dest);

		dev->stats.tx_dropped++;
		dev_kfree_skb(skb);
		kfree_skb(skb);
		return NETDEV_TX_OK;
		}
		}
		@@ -1836,12 +1818,19 @@ static netdev_tx_t vxlan_xmit(struct sk_buff skb, struct net_device dev)
		list_for_each_entry_rcu(rdst, &f->remotes, list) {
		struct sk_buff *skb1;

		if (!fdst) {
		fdst = rdst;
		continue;
		}
		skb1 = skb_clone(skb, GFP_ATOMIC);
		if (skb1)
		vxlan_xmit_one(skb1, dev, rdst, did_rsc);
		}

		dev_kfree_skb(skb);
		if (fdst)
		vxlan_xmit_one(skb, dev, fdst, did_rsc);
		else
		kfree_skb(skb);
		return NETDEV_TX_OK;
		}

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