ila: add checksum neutral ILA translations

Support checksum neutral ILA as described in the ILA draft. The low
order 16 bits of the identifier are used to contain the checksum
adjustment value.

The csum-mode parameter is added to described checksum processing. There
are three values:
 - adjust transport checksum (previous behavior)
 - do checksum neutral mapping
 - do nothing

On output the csum-mode in the ila_params is checked and acted on. If
mode is checksum neutral mapping then to mapping and set C-bit.

On input, C-bit is checked. If it is set checksum-netural mapping is
done (regardless of csum-mode in ila params) and C-bit will be cleared.
If it is not set then action in csum-mode is taken.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 71 insertions, 3 deletions

diff --git a/net/ipv6/ila/ila_common.c b/net/ipv6/ila/ila_common.c
index c3078d0b64e1..0e94042d1289 100644
--- a/net/ipv6/ila/ila_common.c
+++ b/net/ipv6/ila/ila_common.c
@@ -17,21 +17,50 @@ static __wsum get_csum_diff(struct ipv6hdr *ip6h, struct ila_params *p)
 {
 	struct ila_addr *iaddr = ila_a2i(&ip6h->daddr);
 
-	if (iaddr->loc.v64 == p->locator_match.v64)
+	if (p->locator_match.v64)
 		return p->csum_diff;
 	else
 		return compute_csum_diff8((__be32 *)&iaddr->loc,
 					  (__be32 *)&p->locator);
 }
 
-void ila_update_ipv6_locator(struct sk_buff *skb, struct ila_params *p)
+static void ila_csum_do_neutral(struct ila_addr *iaddr,
+				struct ila_params *p)
+{
+	__sum16 *adjust = (__force __sum16 *)&iaddr->ident.v16[3];
+	__wsum diff, fval;
+
+	/* Check if checksum adjust value has been cached */
+	if (p->locator_match.v64) {
+		diff = p->csum_diff;
+	} else {
+		diff = compute_csum_diff8((__be32 *)iaddr,
+					  (__be32 *)&p->locator);
+	}
+
+	fval = (__force __wsum)(ila_csum_neutral_set(iaddr->ident) ?
+			~CSUM_NEUTRAL_FLAG : CSUM_NEUTRAL_FLAG);
+
+	diff = csum_add(diff, fval);
+
+	*adjust = ~csum_fold(csum_add(diff, csum_unfold(*adjust)));
+
+	/* Flip the csum-neutral bit. Either we are doing a SIR->ILA
+	 * translation with ILA_CSUM_NEUTRAL_MAP as the csum_method
+	 * and the C-bit is not set, or we are doing an ILA-SIR
+	 * tranlsation and the C-bit is set.
+	 */
+	iaddr->ident.csum_neutral ^= 1;
+}
+
+static void ila_csum_adjust_transport(struct sk_buff *skb,
+				      struct ila_params *p)
 {
 	__wsum diff;
 	struct ipv6hdr *ip6h = ipv6_hdr(skb);
 	struct ila_addr *iaddr = ila_a2i(&ip6h->daddr);
 	size_t nhoff = sizeof(struct ipv6hdr);
 
-	/* First update checksum */
 	switch (ip6h->nexthdr) {
 	case NEXTHDR_TCP:
 		if (likely(pskb_may_pull(skb, nhoff + sizeof(struct tcphdr)))) {
@@ -74,6 +103,45 @@ void ila_update_ipv6_locator(struct sk_buff *skb, struct ila_params *p)
 	iaddr->loc = p->locator;
 }
 
+void ila_update_ipv6_locator(struct sk_buff *skb, struct ila_params *p)
+{
+	struct ipv6hdr *ip6h = ipv6_hdr(skb);
+	struct ila_addr *iaddr = ila_a2i(&ip6h->daddr);
+
+	/* First deal with the transport checksum */
+	if (ila_csum_neutral_set(iaddr->ident)) {
+		/* C-bit is set in the locator indicating that this
+		 * is a locator being translated to a SIR address.
+		 * Perform (receiver) checksum-neutral translation.
+		 */
+		ila_csum_do_neutral(iaddr, p);
+	} else {
+		switch (p->csum_mode) {
+		case ILA_CSUM_ADJUST_TRANSPORT:
+			ila_csum_adjust_transport(skb, p);
+			break;
+		case ILA_CSUM_NEUTRAL_MAP:
+			ila_csum_do_neutral(iaddr, p);
+			break;
+		case ILA_CSUM_NO_ACTION:
+			break;
+		}
+	}
+
+	/* Now change destination address */
+	iaddr->loc = p->locator;
+}
+
+void ila_init_saved_csum(struct ila_params *p)
+{
+	if (!p->locator_match.v64)
+		return;
+
+	p->csum_diff = compute_csum_diff8(
+				(__be32 *)&p->locator_match,
+				(__be32 *)&p->locator);
+}
+
 static int __init ila_init(void)
 {
 	int ret;