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>

include/uapi/linux/ila.h

@@ -15,6 +15,7 @@ enum {
 	ILA_ATTR_IFINDEX,			/* s32 */
 	ILA_ATTR_DIR,				/* u32 */
 	ILA_ATTR_PAD,
+	ILA_ATTR_CSUM_MODE,			/* u8 */
 
 	__ILA_ATTR_MAX,
 };
@@ -35,4 +36,10 @@ enum {
 #define ILA_DIR_IN	(1 << 0)
 #define ILA_DIR_OUT	(1 << 1)
 
+enum {
+	ILA_CSUM_ADJUST_TRANSPORT,
+	ILA_CSUM_NEUTRAL_MAP,
+	ILA_CSUM_NO_ACTION,
+};
+
 #endif /* _UAPI_LINUX_ILA_H */

net/ipv6/ila/ila.h

@@ -36,11 +36,13 @@ struct ila_identifier {
 	union {
 		struct {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
-			u8 __space:5;
+			u8 __space:4;
+			u8 csum_neutral:1;
 			u8 type:3;
 #elif defined(__BIG_ENDIAN_BITFIELD)
 			u8 type:3;
-			u8 __space:5;
+			u8 csum_neutral:1;
+			u8 __space:4;
 #else
 #error  "Adjust your <asm/byteorder.h> defines"
 #endif
@@ -64,6 +66,8 @@ enum {
 	ILA_ATYPE_RSVD_3,
 };
 
+#define CSUM_NEUTRAL_FLAG	htonl(0x10000000)
+
 struct ila_addr {
 	union {
 		struct in6_addr addr;
@@ -88,6 +92,7 @@ struct ila_params {
 	struct ila_locator locator;
 	struct ila_locator locator_match;
 	__wsum csum_diff;
+	u8 csum_mode;
 };
 
 static inline __wsum compute_csum_diff8(const __be32 *from, const __be32 *to)
@@ -99,8 +104,15 @@ static inline __wsum compute_csum_diff8(const __be32 *from, const __be32 *to)
 	return csum_partial(diff, sizeof(diff), 0);
 }
 
+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_init_saved_csum(struct ila_params *p);
+
 int ila_lwt_init(void);
 void ila_lwt_fini(void);
 int ila_xlat_init(void);

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;

net/ipv6/ila/ila_lwt.c

@@ -53,6 +53,7 @@ static int ila_input(struct sk_buff *skb)
 
 static struct nla_policy ila_nl_policy[ILA_ATTR_MAX + 1] = {
 	[ILA_ATTR_LOCATOR] = { .type = NLA_U64, },
+	[ILA_ATTR_CSUM_MODE] = { .type = NLA_U8, },
 };
 
 static int ila_build_state(struct net_device *dev, struct nlattr *nla,
@@ -79,8 +80,10 @@ static int ila_build_state(struct net_device *dev, struct nlattr *nla,
 
 	iaddr = (struct ila_addr *)&cfg6->fc_dst;
 
-	if (!ila_addr_is_ila(iaddr)) {
-		/* Don't allow setting a translation for a non-ILA address */
+	if (!ila_addr_is_ila(iaddr) || ila_csum_neutral_set(iaddr->ident)) {
+		/* Don't allow translation for a non-ILA address or checksum
+		 * neutral flag to be set.
+		 */
 		return -EINVAL;
 	}
 
@@ -108,6 +111,11 @@ static int ila_build_state(struct net_device *dev, struct nlattr *nla,
 	p->csum_diff = compute_csum_diff8(
 		(__be32 *)&p->locator_match, (__be32 *)&p->locator);
 
+	if (tb[ILA_ATTR_CSUM_MODE])
+		p->csum_mode = nla_get_u8(tb[ILA_ATTR_CSUM_MODE]);
+
+	ila_init_saved_csum(p);
+
 	newts->type = LWTUNNEL_ENCAP_ILA;
 	newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT |
 			LWTUNNEL_STATE_INPUT_REDIRECT;
@@ -125,6 +133,8 @@ static int ila_fill_encap_info(struct sk_buff *skb,
 	if (nla_put_u64_64bit(skb, ILA_ATTR_LOCATOR, (__force u64)p->locator.v64,
 			      ILA_ATTR_PAD))
 		goto nla_put_failure;
+	if (nla_put_u64(skb, ILA_ATTR_CSUM_MODE, (__force u8)p->csum_mode))
+		goto nla_put_failure;
 
 	return 0;
 

net/ipv6/ila/ila_xlat.c

@@ -132,6 +132,7 @@ static struct nla_policy ila_nl_policy[ILA_ATTR_MAX + 1] = {
 	[ILA_ATTR_LOCATOR] = { .type = NLA_U64, },
 	[ILA_ATTR_LOCATOR_MATCH] = { .type = NLA_U64, },
 	[ILA_ATTR_IFINDEX] = { .type = NLA_U32, },
+	[ILA_ATTR_CSUM_MODE] = { .type = NLA_U8, },
 };
 
 static int parse_nl_config(struct genl_info *info,
@@ -147,6 +148,9 @@ static int parse_nl_config(struct genl_info *info,
 		xp->ip.locator_match.v64 = (__force __be64)nla_get_u64(
 			info->attrs[ILA_ATTR_LOCATOR_MATCH]);
 
+	if (info->attrs[ILA_ATTR_CSUM_MODE])
+		xp->ip.csum_mode = nla_get_u8(info->attrs[ILA_ATTR_CSUM_MODE]);
+
 	if (info->attrs[ILA_ATTR_IFINDEX])
 		xp->ifindex = nla_get_s32(info->attrs[ILA_ATTR_IFINDEX]);
 
@@ -249,14 +253,9 @@ static int ila_add_mapping(struct net *net, struct ila_xlat_params *xp)
 	if (!ila)
 		return -ENOMEM;
 
-	ila->xp = *xp;
+	ila_init_saved_csum(&xp->ip);
 
-	/* Precompute checksum difference for translation since we
-	 * know both the old identifier and the new one.
-	 */
-	ila->xp.ip.csum_diff = compute_csum_diff8(
-		(__be32 *)&xp->ip.locator_match,
-		(__be32 *)&xp->ip.locator);
+	ila->xp = *xp;
 
 	order = ila_order(ila);
 
@@ -408,7 +407,8 @@ static int ila_fill_info(struct ila_map *ila, struct sk_buff *msg)
 	    nla_put_u64_64bit(msg, ILA_ATTR_LOCATOR_MATCH,
 			      (__force u64)ila->xp.ip.locator_match.v64,
 			      ILA_ATTR_PAD) ||
-	    nla_put_s32(msg, ILA_ATTR_IFINDEX, ila->xp.ifindex))
+	    nla_put_s32(msg, ILA_ATTR_IFINDEX, ila->xp.ifindex) ||
+	    nla_put_u32(msg, ILA_ATTR_CSUM_MODE, ila->xp.ip.csum_mode))
 		return -1;
 
 	return 0;