[ovs-dev] [PATCH] compat: Remove rpl_dev_queue_xmit() backport.

[Joe Stringer]

The MPLS portions of this were inadvertently broken in v2.4 due to
433637881ca5 ("datapath: define compat __skb_gso_segment()") which
inverts the supports_mpls_gso() logic, then when rpl_dev_queue_xmit()
backport dropped its VLAN portion in v2.6, the whole function became a
no-op - since b63bf2488209 ("datapath: remove VLAN compat code from GSO").

Apparently the MPLS side of this code never worked in a released version
of OVS and no-one noticed, so remove it.

Signed-off-by: Joe Stringer <joe at ovn.org>
---
CC: Simon Horman <horms at verge.net.au>

Simon, I'm not sure what the repercussions are of this but by my reading
of the code the extra skb_gso_segment compat code here is never invoked
anyway so I figure we can just drop it. Looks like it might've been
fine when originally submitted, but by the time v2.4 came out it was
already nerfed >.<

That said, if we just need to fix the version check to get it working
again then that's an option. Also, I see that the upstream commit
48d2ab609b6b ("net: mpls: Fixups for GSO") will further change the way
that OVS deals with MPLS GSO, so perhaps we'll actually need to bring
back a backport for handling those cases, when that patch is backported
to the OVS tree.
---
 datapath/linux/compat/gso.c                     | 91 -------------------------
 datapath/linux/compat/include/linux/netdevice.h |  5 --
 2 files changed, 96 deletions(-)

diff --git a/datapath/linux/compat/gso.c b/datapath/linux/compat/gso.c
index 48a56b9f5d5f..2638f1114ede 100644
--- a/datapath/linux/compat/gso.c
+++ b/datapath/linux/compat/gso.c
@@ -41,97 +41,6 @@
 
 #include "gso.h"
 
-#ifdef OVS_USE_COMPAT_GSO_SEGMENTATION
-/* Strictly this is not needed and will be optimised out
- * as this code is guarded by if LINUX_VERSION_CODE < KERNEL_VERSION(3,19,0).
- * It is here to make things explicit should the compatibility
- * code be extended in some way prior extending its life-span
- * beyond v3.19.
- */
-static bool supports_mpls_gso(void)
-{
-/* MPLS GSO was introduced in v3.11, however it was not correctly
- * activated using mpls_features until v3.19. */
-#ifdef OVS_USE_COMPAT_GSO_SEGMENTATION
-	return true;
-#else
-	return false;
-#endif
-}
-
-int rpl_dev_queue_xmit(struct sk_buff *skb)
-{
-#undef dev_queue_xmit
-	int err = -ENOMEM;
-	bool mpls;
-
-	mpls = false;
-
-	/* Avoid traversing any VLAN tags that are present to determine if
-	 * the ethtype is MPLS. Instead compare the mac_len (end of L2) and
-	 * skb_network_offset() (beginning of L3) whose inequality will
-	 * indicate the presence of an MPLS label stack. */
-	if (skb->mac_len != skb_network_offset(skb) && !supports_mpls_gso())
-		mpls = true;
-
-	if (mpls) {
-		int features;
-
-		features = netif_skb_features(skb);
-
-		/* As of v3.11 the kernel provides an mpls_features field in
-		 * struct net_device which allows devices to advertise which
-		 * features its supports for MPLS. This value defaults to
-		 * NETIF_F_SG and as of v3.19.
-		 *
-		 * This compatibility code is intended for kernels older
-		 * than v3.19 that do not support MPLS GSO and do not
-		 * use mpls_features. Thus this code uses NETIF_F_SG
-		 * directly in place of mpls_features.
-		 */
-		if (mpls)
-			features &= NETIF_F_SG;
-
-		if (netif_needs_gso(skb, features)) {
-			struct sk_buff *nskb;
-
-			nskb = skb_gso_segment(skb, features);
-			if (!nskb) {
-				if (unlikely(skb_cloned(skb) &&
-				    pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
-					goto drop;
-
-				skb_shinfo(skb)->gso_type &= ~SKB_GSO_DODGY;
-				goto xmit;
-			}
-
-			if (IS_ERR(nskb)) {
-				err = PTR_ERR(nskb);
-				goto drop;
-			}
-			consume_skb(skb);
-			skb = nskb;
-
-			do {
-				nskb = skb->next;
-				skb->next = NULL;
-				err = dev_queue_xmit(skb);
-				skb = nskb;
-			} while (skb);
-
-			return err;
-		}
-	}
-xmit:
-	return dev_queue_xmit(skb);
-
-drop:
-	kfree_skb(skb);
-	return err;
-}
-EXPORT_SYMBOL_GPL(rpl_dev_queue_xmit);
-#endif /* OVS_USE_COMPAT_GSO_SEGMENTATION */
-
 #ifndef USE_UPSTREAM_TUNNEL_GSO
 static __be16 __skb_network_protocol(struct sk_buff *skb)
 {
diff --git a/datapath/linux/compat/include/linux/netdevice.h b/datapath/linux/compat/include/linux/netdevice.h
index 75315dc16e02..dc05ee9a9ca7 100644
--- a/datapath/linux/compat/include/linux/netdevice.h
+++ b/datapath/linux/compat/include/linux/netdevice.h
@@ -111,11 +111,6 @@ static inline int rpl_netdev_master_upper_dev_link(struct net_device *dev,
 
 #endif
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(3,16,0)
-#define dev_queue_xmit rpl_dev_queue_xmit
-int rpl_dev_queue_xmit(struct sk_buff *skb);
-#endif
-
 #if LINUX_VERSION_CODE < KERNEL_VERSION(3,11,0)
 static inline struct net_device *rpl_netdev_notifier_info_to_dev(void *info)
 {
-- 
2.11.0