netdev - [PATCH net-next] ila: Perform only one translation in forwarding path

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Date:	Tue, 7 Jun 2016 16:09:44 -0700
From:	Tom Herbert <tom@...bertland.com>
To:	<davem@...emloft.net>, <netdev@...r.kernel.org>
CC:	<kernel-team@...com>
Subject: [PATCH net-next] ila: Perform only one translation in forwarding path

When setting up ILA in a router we noticed that the the encapsulation
is invoked twice: once in the route input path and again upon route
output. To resolve this we add a flag set_csum_neutral for the
ila_update_ipv6_locator. If this flag is set and the checksum
neutral bit is also set we assume that checksum-neutral translation
has already been performed and take no further action. The
flag is set only in ila_output path. The flag is not set for ila_input and
ila_xlat.

Tested:

Used 3 netns to set to emulate a router and two hosts. The router
translates SIR addresses between the two destinations in other two netns.
Verified ping and netperf are functional.

Signed-off-by: Tom Herbert <tom@...bertland.com>
---
 net/ipv6/ila/ila.h        | 3 ++-
 net/ipv6/ila/ila_common.c | 6 ++++--
 net/ipv6/ila/ila_lwt.c    | 4 ++--
 net/ipv6/ila/ila_xlat.c   | 8 ++++----
 4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/ila/ila.h b/net/ipv6/ila/ila.h
index d08fd2d..e0170f6 100644
--- a/net/ipv6/ila/ila.h
+++ b/net/ipv6/ila/ila.h
@@ -109,7 +109,8 @@ static inline bool ila_csum_neutral_set(struct ila_identifier ident)
 	return !!(ident.csum_neutral);
 }
 
-void ila_update_ipv6_locator(struct sk_buff *skb, struct ila_params *p);
+void ila_update_ipv6_locator(struct sk_buff *skb, struct ila_params *p,
+			     bool set_csum_neutral);
 
 void ila_init_saved_csum(struct ila_params *p);
 
diff --git a/net/ipv6/ila/ila_common.c b/net/ipv6/ila/ila_common.c
index 0e94042..b3d00be 100644
--- a/net/ipv6/ila/ila_common.c
+++ b/net/ipv6/ila/ila_common.c
@@ -103,7 +103,8 @@ static void ila_csum_adjust_transport(struct sk_buff *skb,
 	iaddr->loc = p->locator;
 }
 
-void ila_update_ipv6_locator(struct sk_buff *skb, struct ila_params *p)
+void ila_update_ipv6_locator(struct sk_buff *skb, struct ila_params *p,
+			     bool set_csum_neutral)
 {
 	struct ipv6hdr *ip6h = ipv6_hdr(skb);
 	struct ila_addr *iaddr = ila_a2i(&ip6h->daddr);
@@ -114,7 +115,8 @@ void ila_update_ipv6_locator(struct sk_buff *skb, struct ila_params *p)
 		 * is a locator being translated to a SIR address.
 		 * Perform (receiver) checksum-neutral translation.
 		 */
-		ila_csum_do_neutral(iaddr, p);
+		if (!set_csum_neutral)
+			ila_csum_do_neutral(iaddr, p);
 	} else {
 		switch (p->csum_mode) {
 		case ILA_CSUM_ADJUST_TRANSPORT:
diff --git a/net/ipv6/ila/ila_lwt.c b/net/ipv6/ila/ila_lwt.c
index 1dfb641..c8314c6 100644
--- a/net/ipv6/ila/ila_lwt.c
+++ b/net/ipv6/ila/ila_lwt.c
@@ -26,7 +26,7 @@ static int ila_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 	if (skb->protocol != htons(ETH_P_IPV6))
 		goto drop;
 
-	ila_update_ipv6_locator(skb, ila_params_lwtunnel(dst->lwtstate));
+	ila_update_ipv6_locator(skb, ila_params_lwtunnel(dst->lwtstate), true);
 
 	return dst->lwtstate->orig_output(net, sk, skb);
 
@@ -42,7 +42,7 @@ static int ila_input(struct sk_buff *skb)
 	if (skb->protocol != htons(ETH_P_IPV6))
 		goto drop;
 
-	ila_update_ipv6_locator(skb, ila_params_lwtunnel(dst->lwtstate));
+	ila_update_ipv6_locator(skb, ila_params_lwtunnel(dst->lwtstate), false);
 
 	return dst->lwtstate->orig_input(skb);
 
diff --git a/net/ipv6/ila/ila_xlat.c b/net/ipv6/ila/ila_xlat.c
index a90e572..e6eca5f 100644
--- a/net/ipv6/ila/ila_xlat.c
+++ b/net/ipv6/ila/ila_xlat.c
@@ -210,14 +210,14 @@ static void ila_free_cb(void *ptr, void *arg)
 	}
 }
 
-static int ila_xlat_addr(struct sk_buff *skb);
+static int ila_xlat_addr(struct sk_buff *skb, bool set_csum_neutral);
 
 static unsigned int
 ila_nf_input(void *priv,
 	     struct sk_buff *skb,
 	     const struct nf_hook_state *state)
 {
-	ila_xlat_addr(skb);
+	ila_xlat_addr(skb, false);
 	return NF_ACCEPT;
 }
 
@@ -597,7 +597,7 @@ static struct pernet_operations ila_net_ops = {
 	.size = sizeof(struct ila_net),
 };
 
-static int ila_xlat_addr(struct sk_buff *skb)
+static int ila_xlat_addr(struct sk_buff *skb, bool set_csum_neutral)
 {
 	struct ila_map *ila;
 	struct ipv6hdr *ip6h = ipv6_hdr(skb);
@@ -616,7 +616,7 @@ static int ila_xlat_addr(struct sk_buff *skb)
 
 	ila = ila_lookup_wildcards(iaddr, skb->dev->ifindex, ilan);
 	if (ila)
-		ila_update_ipv6_locator(skb, &ila->xp.ip);
+		ila_update_ipv6_locator(skb, &ila->xp.ip, set_csum_neutral);
 
 	rcu_read_unlock();
 
-- 
2.8.0.rc2