71 lines
2.7 KiB
Diff
71 lines
2.7 KiB
Diff
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From 30b678d844af3305cda5953467005cebb5d7b687 Mon Sep 17 00:00:00 2001
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From: Ben Hutchings <bhutchings@solarflare.com>
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Date: Mon, 30 Jul 2012 15:57:00 +0000
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Subject: [PATCH] net: Allow driver to limit number of GSO segments per skb
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A peer (or local user) may cause TCP to use a nominal MSS of as little
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as 88 (actual MSS of 76 with timestamps). Given that we have a
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sufficiently prodigious local sender and the peer ACKs quickly enough,
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it is nevertheless possible to grow the window for such a connection
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to the point that we will try to send just under 64K at once. This
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results in a single skb that expands to 861 segments.
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In some drivers with TSO support, such an skb will require hundreds of
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DMA descriptors; a substantial fraction of a TX ring or even more than
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a full ring. The TX queue selected for the skb may stall and trigger
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the TX watchdog repeatedly (since the problem skb will be retried
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after the TX reset). This particularly affects sfc, for which the
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issue is designated as CVE-2012-3412.
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Therefore:
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1. Add the field net_device::gso_max_segs holding the device-specific
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limit.
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2. In netif_skb_features(), if the number of segments is too high then
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mask out GSO features to force fall back to software GSO.
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Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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include/linux/netdevice.h | 2 ++
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net/core/dev.c | 4 ++++
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2 files changed, 6 insertions(+), 0 deletions(-)
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diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
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index eb06e58..a9db4f3 100644
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--- a/include/linux/netdevice.h
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+++ b/include/linux/netdevice.h
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@@ -1300,6 +1300,8 @@ struct net_device {
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/* for setting kernel sock attribute on TCP connection setup */
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#define GSO_MAX_SIZE 65536
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unsigned int gso_max_size;
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+#define GSO_MAX_SEGS 65535
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+ u16 gso_max_segs;
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#ifdef CONFIG_DCB
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/* Data Center Bridging netlink ops */
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diff --git a/net/core/dev.c b/net/core/dev.c
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index 0cb3fe8..f91abf8 100644
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -2134,6 +2134,9 @@ netdev_features_t netif_skb_features(struct sk_buff *skb)
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__be16 protocol = skb->protocol;
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netdev_features_t features = skb->dev->features;
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+ if (skb_shinfo(skb)->gso_segs > skb->dev->gso_max_segs)
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+ features &= ~NETIF_F_GSO_MASK;
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+
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if (protocol == htons(ETH_P_8021Q)) {
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struct vlan_ethhdr *veh = (struct vlan_ethhdr *)skb->data;
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protocol = veh->h_vlan_encapsulated_proto;
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@@ -5986,6 +5989,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
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dev_net_set(dev, &init_net);
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dev->gso_max_size = GSO_MAX_SIZE;
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+ dev->gso_max_segs = GSO_MAX_SEGS;
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INIT_LIST_HEAD(&dev->napi_list);
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INIT_LIST_HEAD(&dev->unreg_list);
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--
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1.7.7.6
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