Merge branch 'xfrm: policy: replace session decode with flow dissector'

Florian Westphal says:

============
Remove the ipv4+ipv6 session decode functions and use generic flow
dissector to populate the flowi for the policy lookup.

Changes since v2:
- first patch broke CONFIG_XFRM=n builds

Changes since v1:
- Can't use skb_flow_dissect(), we might see skbs that have neither
  skb->sk nor skb->dev set. Flow dissector WARN()s in this case, it
  tries to check for a bpf program assigned in that net namespace.

Add a preparation patch to pass down 'struct net' in
xfrm_decode_session so its available for use in patch 3.

Changes since RFC:

- Drop mobility header support.  I don't think that anyone uses
  this.  MOBIKE doesn't appear to need this either.
- Drop fl6->flowlabel assignment, original code leaves it as 0.

There is no reason for this change other than to remove code.
============

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

include/net/xfrm.h

@@ -1207,20 +1207,20 @@ static inline int xfrm6_policy_check_reverse(struct sock *sk, int dir,
 	return __xfrm_policy_check2(sk, dir, skb, AF_INET6, 1);
 }
 
-int __xfrm_decode_session(struct sk_buff *skb, struct flowi *fl,
+int __xfrm_decode_session(struct net *net, struct sk_buff *skb, struct flowi *fl,
 			  unsigned int family, int reverse);
 
-static inline int xfrm_decode_session(struct sk_buff *skb, struct flowi *fl,
+static inline int xfrm_decode_session(struct net *net, struct sk_buff *skb, struct flowi *fl,
 				      unsigned int family)
 {
-	return __xfrm_decode_session(skb, fl, family, 0);
+	return __xfrm_decode_session(net, skb, fl, family, 0);
 }
 
-static inline int xfrm_decode_session_reverse(struct sk_buff *skb,
+static inline int xfrm_decode_session_reverse(struct net *net, struct sk_buff *skb,
 					      struct flowi *fl,
 					      unsigned int family)
 {
-	return __xfrm_decode_session(skb, fl, family, 1);
+	return __xfrm_decode_session(net, skb, fl, family, 1);
 }
 
 int __xfrm_route_forward(struct sk_buff *skb, unsigned short family);
@@ -1296,7 +1296,7 @@ static inline int xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *sk
 {
 	return 1;
 }
-static inline int xfrm_decode_session_reverse(struct sk_buff *skb,
+static inline int xfrm_decode_session_reverse(struct net *net, struct sk_buff *skb,
 					      struct flowi *fl,
 					      unsigned int family)
 {

net/ipv4/icmp.c

@@ -517,7 +517,7 @@ static struct rtable *icmp_route_lookup(struct net *net,
 	} else
 		return rt;
 
-	err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
+	err = xfrm_decode_session_reverse(net, skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
 	if (err)
 		goto relookup_failed;
 

net/ipv4/ip_vti.c

@@ -288,11 +288,11 @@ static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
 		memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
-		xfrm_decode_session(skb, &fl, AF_INET);
+		xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET);
 		break;
 	case htons(ETH_P_IPV6):
 		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
-		xfrm_decode_session(skb, &fl, AF_INET6);
+		xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET6);
 		break;
 	default:
 		goto tx_err;

net/ipv4/netfilter.c

@@ -62,7 +62,7 @@ int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, un
 
 #ifdef CONFIG_XFRM
 	if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
-	    xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
+	    xfrm_decode_session(net, skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
 		struct dst_entry *dst = skb_dst(skb);
 		skb_dst_set(skb, NULL);
 		dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0);

net/ipv6/icmp.c

@@ -385,7 +385,7 @@ static struct dst_entry *icmpv6_route_lookup(struct net *net,
 			return dst;
 	}
 
-	err = xfrm_decode_session_reverse(skb, flowi6_to_flowi(&fl2), AF_INET6);
+	err = xfrm_decode_session_reverse(net, skb, flowi6_to_flowi(&fl2), AF_INET6);
 	if (err)
 		goto relookup_failed;
 

net/ipv6/ip6_vti.c

@@ -569,11 +569,11 @@ vti6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 			goto tx_err;
 
 		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
-		xfrm_decode_session(skb, &fl, AF_INET6);
+		xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET6);
 		break;
 	case htons(ETH_P_IP):
 		memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
-		xfrm_decode_session(skb, &fl, AF_INET);
+		xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET);
 		break;
 	default:
 		goto tx_err;

net/ipv6/netfilter.c

@@ -61,7 +61,7 @@ int ip6_route_me_harder(struct net *net, struct sock *sk_partial, struct sk_buff
 
 #ifdef CONFIG_XFRM
 	if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
-	    xfrm_decode_session(skb, flowi6_to_flowi(&fl6), AF_INET6) == 0) {
+	    xfrm_decode_session(net, skb, flowi6_to_flowi(&fl6), AF_INET6) == 0) {
 		skb_dst_set(skb, NULL);
 		dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), sk, 0);
 		if (IS_ERR(dst))

net/netfilter/nf_nat_proto.c

@@ -668,7 +668,7 @@ static int nf_xfrm_me_harder(struct net *net, struct sk_buff *skb, unsigned int
 	struct flowi fl;
 	int err;
 
-	err = xfrm_decode_session(skb, &fl, family);
+	err = xfrm_decode_session(net, skb, &fl, family);
 	if (err < 0)
 		return err;
 

net/xfrm/xfrm_interface_core.c

@@ -538,7 +538,7 @@ static netdev_tx_t xfrmi_xmit(struct sk_buff *skb, struct net_device *dev)
 	switch (skb->protocol) {
 	case htons(ETH_P_IPV6):
 		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
-		xfrm_decode_session(skb, &fl, AF_INET6);
+		xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET6);
 		if (!dst) {
 			fl.u.ip6.flowi6_oif = dev->ifindex;
 			fl.u.ip6.flowi6_flags |= FLOWI_FLAG_ANYSRC;
@@ -553,7 +553,7 @@ static netdev_tx_t xfrmi_xmit(struct sk_buff *skb, struct net_device *dev)
 		break;
 	case htons(ETH_P_IP):
 		memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
-		xfrm_decode_session(skb, &fl, AF_INET);
+		xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET);
 		if (!dst) {
 			struct rtable *rt;
 

net/xfrm/xfrm_policy.c

@@ -149,6 +149,21 @@ struct xfrm_pol_inexact_candidates {
 	struct hlist_head *res[XFRM_POL_CAND_MAX];
 };
 
+struct xfrm_flow_keys {
+	struct flow_dissector_key_basic basic;
+	struct flow_dissector_key_control control;
+	union {
+		struct flow_dissector_key_ipv4_addrs ipv4;
+		struct flow_dissector_key_ipv6_addrs ipv6;
+	} addrs;
+	struct flow_dissector_key_ip ip;
+	struct flow_dissector_key_icmp icmp;
+	struct flow_dissector_key_ports ports;
+	struct flow_dissector_key_keyid gre;
+};
+
+static struct flow_dissector xfrm_session_dissector __ro_after_init;
+
 static DEFINE_SPINLOCK(xfrm_if_cb_lock);
 static struct xfrm_if_cb const __rcu *xfrm_if_cb __read_mostly;
 
@@ -2853,7 +2868,7 @@ static void xfrm_policy_queue_process(struct timer_list *t)
 	/* Fixup the mark to support VTI. */
 	skb_mark = skb->mark;
 	skb->mark = pol->mark.v;
-	xfrm_decode_session(skb, &fl, dst->ops->family);
+	xfrm_decode_session(net, skb, &fl, dst->ops->family);
 	skb->mark = skb_mark;
 	spin_unlock(&pq->hold_queue.lock);
 
@@ -2889,7 +2904,7 @@ static void xfrm_policy_queue_process(struct timer_list *t)
 		/* Fixup the mark to support VTI. */
 		skb_mark = skb->mark;
 		skb->mark = pol->mark.v;
-		xfrm_decode_session(skb, &fl, skb_dst(skb)->ops->family);
+		xfrm_decode_session(net, skb, &fl, skb_dst(skb)->ops->family);
 		skb->mark = skb_mark;
 
 		dst_hold(xfrm_dst_path(skb_dst(skb)));
@@ -3367,209 +3382,92 @@ xfrm_policy_ok(const struct xfrm_tmpl *tmpl, const struct sec_path *sp, int star
 }
 
 static void
-decode_session4(struct sk_buff *skb, struct flowi *fl, bool reverse)
+decode_session4(const struct xfrm_flow_keys *flkeys, struct flowi *fl, bool reverse)
 {
-	const struct iphdr *iph = ip_hdr(skb);
-	int ihl = iph->ihl;
-	u8 *xprth = skb_network_header(skb) + ihl * 4;
 	struct flowi4 *fl4 = &fl->u.ip4;
-	int oif = 0;
-
-	if (skb_dst(skb) && skb_dst(skb)->dev)
-		oif = skb_dst(skb)->dev->ifindex;
 
 	memset(fl4, 0, sizeof(struct flowi4));
-	fl4->flowi4_mark = skb->mark;
-	fl4->flowi4_oif = reverse ? skb->skb_iif : oif;
 
-	fl4->flowi4_proto = iph->protocol;
-	fl4->daddr = reverse ? iph->saddr : iph->daddr;
-	fl4->saddr = reverse ? iph->daddr : iph->saddr;
-	fl4->flowi4_tos = iph->tos & ~INET_ECN_MASK;
-
-	if (!ip_is_fragment(iph)) {
-		switch (iph->protocol) {
-		case IPPROTO_UDP:
-		case IPPROTO_UDPLITE:
-		case IPPROTO_TCP:
-		case IPPROTO_SCTP:
-		case IPPROTO_DCCP:
-			if (xprth + 4 < skb->data ||
-			    pskb_may_pull(skb, xprth + 4 - skb->data)) {
-				__be16 *ports;
-
-				xprth = skb_network_header(skb) + ihl * 4;
-				ports = (__be16 *)xprth;
-
-				fl4->fl4_sport = ports[!!reverse];
-				fl4->fl4_dport = ports[!reverse];
-			}
-			break;
-		case IPPROTO_ICMP:
-			if (xprth + 2 < skb->data ||
-			    pskb_may_pull(skb, xprth + 2 - skb->data)) {
-				u8 *icmp;
-
-				xprth = skb_network_header(skb) + ihl * 4;
-				icmp = xprth;
-
-				fl4->fl4_icmp_type = icmp[0];
-				fl4->fl4_icmp_code = icmp[1];
-			}
-			break;
-		case IPPROTO_GRE:
-			if (xprth + 12 < skb->data ||
-			    pskb_may_pull(skb, xprth + 12 - skb->data)) {
-				__be16 *greflags;
-				__be32 *gre_hdr;
-
-				xprth = skb_network_header(skb) + ihl * 4;
-				greflags = (__be16 *)xprth;
-				gre_hdr = (__be32 *)xprth;
-
-				if (greflags[0] & GRE_KEY) {
-					if (greflags[0] & GRE_CSUM)
-						gre_hdr++;
-					fl4->fl4_gre_key = gre_hdr[1];
-				}
-			}
-			break;
-		default:
-			break;
-		}
+	if (reverse) {
+		fl4->saddr = flkeys->addrs.ipv4.dst;
+		fl4->daddr = flkeys->addrs.ipv4.src;
+		fl4->fl4_sport = flkeys->ports.dst;
+		fl4->fl4_dport = flkeys->ports.src;
+	} else {
+		fl4->saddr = flkeys->addrs.ipv4.src;
+		fl4->daddr = flkeys->addrs.ipv4.dst;
+		fl4->fl4_sport = flkeys->ports.src;
+		fl4->fl4_dport = flkeys->ports.dst;
 	}
+
+	fl4->flowi4_proto = flkeys->basic.ip_proto;
+	fl4->flowi4_tos = flkeys->ip.tos;
+	fl4->fl4_icmp_type = flkeys->icmp.type;
+	fl4->fl4_icmp_type = flkeys->icmp.code;
+	fl4->fl4_gre_key = flkeys->gre.keyid;
 }
 
 #if IS_ENABLED(CONFIG_IPV6)
 static void
-decode_session6(struct sk_buff *skb, struct flowi *fl, bool reverse)
+decode_session6(const struct xfrm_flow_keys *flkeys, struct flowi *fl, bool reverse)
 {
 	struct flowi6 *fl6 = &fl->u.ip6;
-	int onlyproto = 0;
-	const struct ipv6hdr *hdr = ipv6_hdr(skb);
-	u32 offset = sizeof(*hdr);
-	struct ipv6_opt_hdr *exthdr;
-	const unsigned char *nh = skb_network_header(skb);
-	u16 nhoff = IP6CB(skb)->nhoff;
-	int oif = 0;
-	u8 nexthdr;
-
-	if (!nhoff)
-		nhoff = offsetof(struct ipv6hdr, nexthdr);
-
-	nexthdr = nh[nhoff];
-
-	if (skb_dst(skb) && skb_dst(skb)->dev)
-		oif = skb_dst(skb)->dev->ifindex;
 
 	memset(fl6, 0, sizeof(struct flowi6));
-	fl6->flowi6_mark = skb->mark;
-	fl6->flowi6_oif = reverse ? skb->skb_iif : oif;
 
-	fl6->daddr = reverse ? hdr->saddr : hdr->daddr;
-	fl6->saddr = reverse ? hdr->daddr : hdr->saddr;
-
-	while (nh + offset + sizeof(*exthdr) < skb->data ||
-	       pskb_may_pull(skb, nh + offset + sizeof(*exthdr) - skb->data)) {
-		nh = skb_network_header(skb);
-		exthdr = (struct ipv6_opt_hdr *)(nh + offset);
-
-		switch (nexthdr) {
-		case NEXTHDR_FRAGMENT:
-			onlyproto = 1;
-			fallthrough;
-		case NEXTHDR_ROUTING:
-		case NEXTHDR_HOP:
-		case NEXTHDR_DEST:
-			offset += ipv6_optlen(exthdr);
-			nexthdr = exthdr->nexthdr;
-			break;
-		case IPPROTO_UDP:
-		case IPPROTO_UDPLITE:
-		case IPPROTO_TCP:
-		case IPPROTO_SCTP:
-		case IPPROTO_DCCP:
-			if (!onlyproto && (nh + offset + 4 < skb->data ||
-			     pskb_may_pull(skb, nh + offset + 4 - skb->data))) {
-				__be16 *ports;
-
-				nh = skb_network_header(skb);
-				ports = (__be16 *)(nh + offset);
-				fl6->fl6_sport = ports[!!reverse];
-				fl6->fl6_dport = ports[!reverse];
-			}
-			fl6->flowi6_proto = nexthdr;
-			return;
-		case IPPROTO_ICMPV6:
-			if (!onlyproto && (nh + offset + 2 < skb->data ||
-			    pskb_may_pull(skb, nh + offset + 2 - skb->data))) {
-				u8 *icmp;
-
-				nh = skb_network_header(skb);
-				icmp = (u8 *)(nh + offset);
-				fl6->fl6_icmp_type = icmp[0];
-				fl6->fl6_icmp_code = icmp[1];
-			}
-			fl6->flowi6_proto = nexthdr;
-			return;
-		case IPPROTO_GRE:
-			if (!onlyproto &&
-			    (nh + offset + 12 < skb->data ||
-			     pskb_may_pull(skb, nh + offset + 12 - skb->data))) {
-				struct gre_base_hdr *gre_hdr;
-				__be32 *gre_key;
-
-				nh = skb_network_header(skb);
-				gre_hdr = (struct gre_base_hdr *)(nh + offset);
-				gre_key = (__be32 *)(gre_hdr + 1);
-
-				if (gre_hdr->flags & GRE_KEY) {
-					if (gre_hdr->flags & GRE_CSUM)
-						gre_key++;
-					fl6->fl6_gre_key = *gre_key;
-				}
-			}
-			fl6->flowi6_proto = nexthdr;
-			return;
-
-#if IS_ENABLED(CONFIG_IPV6_MIP6)
-		case IPPROTO_MH:
-			offset += ipv6_optlen(exthdr);
-			if (!onlyproto && (nh + offset + 3 < skb->data ||
-			    pskb_may_pull(skb, nh + offset + 3 - skb->data))) {
-				struct ip6_mh *mh;
-
-				nh = skb_network_header(skb);
-				mh = (struct ip6_mh *)(nh + offset);
-				fl6->fl6_mh_type = mh->ip6mh_type;
-			}
-			fl6->flowi6_proto = nexthdr;
-			return;
-#endif
-		default:
-			fl6->flowi6_proto = nexthdr;
-			return;
-		}
+	if (reverse) {
+		fl6->saddr = flkeys->addrs.ipv6.dst;
+		fl6->daddr = flkeys->addrs.ipv6.src;
+		fl6->fl6_sport = flkeys->ports.dst;
+		fl6->fl6_dport = flkeys->ports.src;
+	} else {
+		fl6->saddr = flkeys->addrs.ipv6.src;
+		fl6->daddr = flkeys->addrs.ipv6.dst;
+		fl6->fl6_sport = flkeys->ports.src;
+		fl6->fl6_dport = flkeys->ports.dst;
 	}
+
+	fl6->flowi6_proto = flkeys->basic.ip_proto;
+	fl6->fl6_icmp_type = flkeys->icmp.type;
+	fl6->fl6_icmp_type = flkeys->icmp.code;
+	fl6->fl6_gre_key = flkeys->gre.keyid;
 }
 #endif
 
-int __xfrm_decode_session(struct sk_buff *skb, struct flowi *fl,
+int __xfrm_decode_session(struct net *net, struct sk_buff *skb, struct flowi *fl,
 			  unsigned int family, int reverse)
 {
+	struct xfrm_flow_keys flkeys;
+
+	memset(&flkeys, 0, sizeof(flkeys));
+	__skb_flow_dissect(net, skb, &xfrm_session_dissector, &flkeys,
+			   NULL, 0, 0, 0, FLOW_DISSECTOR_F_STOP_AT_ENCAP);
+
 	switch (family) {
 	case AF_INET:
-		decode_session4(skb, fl, reverse);
+		decode_session4(&flkeys, fl, reverse);
 		break;
 #if IS_ENABLED(CONFIG_IPV6)
 	case AF_INET6:
-		decode_session6(skb, fl, reverse);
+		decode_session6(&flkeys, fl, reverse);
 		break;
 #endif
 	default:
 		return -EAFNOSUPPORT;
 	}
 
+	fl->flowi_mark = skb->mark;
+	if (reverse) {
+		fl->flowi_oif = skb->skb_iif;
+	} else {
+		int oif = 0;
+
+		if (skb_dst(skb) && skb_dst(skb)->dev)
+			oif = skb_dst(skb)->dev->ifindex;
+
+		fl->flowi_oif = oif;
+	}
+
 	return security_xfrm_decode_session(skb, &fl->flowi_secid);
 }
 EXPORT_SYMBOL(__xfrm_decode_session);
@@ -3618,7 +3516,7 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
 	reverse = dir & ~XFRM_POLICY_MASK;
 	dir &= XFRM_POLICY_MASK;
 
-	if (__xfrm_decode_session(skb, &fl, family, reverse) < 0) {
+	if (__xfrm_decode_session(net, skb, &fl, family, reverse) < 0) {
 		XFRM_INC_STATS(net, LINUX_MIB_XFRMINHDRERROR);
 		return 0;
 	}
@@ -3774,7 +3672,7 @@ int __xfrm_route_forward(struct sk_buff *skb, unsigned short family)
 	struct dst_entry *dst;
 	int res = 1;
 
-	if (xfrm_decode_session(skb, &fl, family) < 0) {
+	if (xfrm_decode_session(net, skb, &fl, family) < 0) {
 		XFRM_INC_STATS(net, LINUX_MIB_XFRMFWDHDRERROR);
 		return 0;
 	}
@@ -4253,8 +4151,47 @@ static struct pernet_operations __net_initdata xfrm_net_ops = {
 	.exit = xfrm_net_exit,
 };
 
+static const struct flow_dissector_key xfrm_flow_dissector_keys[] = {
+	{
+		.key_id = FLOW_DISSECTOR_KEY_CONTROL,
+		.offset = offsetof(struct xfrm_flow_keys, control),
+	},
+	{
+		.key_id = FLOW_DISSECTOR_KEY_BASIC,
+		.offset = offsetof(struct xfrm_flow_keys, basic),
+	},
+	{
+		.key_id = FLOW_DISSECTOR_KEY_IPV4_ADDRS,
+		.offset = offsetof(struct xfrm_flow_keys, addrs.ipv4),
+	},
+	{
+		.key_id = FLOW_DISSECTOR_KEY_IPV6_ADDRS,
+		.offset = offsetof(struct xfrm_flow_keys, addrs.ipv6),
+	},
+	{
+		.key_id = FLOW_DISSECTOR_KEY_PORTS,
+		.offset = offsetof(struct xfrm_flow_keys, ports),
+	},
+	{
+		.key_id = FLOW_DISSECTOR_KEY_GRE_KEYID,
+		.offset = offsetof(struct xfrm_flow_keys, gre),
+	},
+	{
+		.key_id = FLOW_DISSECTOR_KEY_IP,
+		.offset = offsetof(struct xfrm_flow_keys, ip),
+	},
+	{
+		.key_id = FLOW_DISSECTOR_KEY_ICMP,
+		.offset = offsetof(struct xfrm_flow_keys, icmp),
+	},
+};
+
 void __init xfrm_init(void)
 {
+	skb_flow_dissector_init(&xfrm_session_dissector,
+				xfrm_flow_dissector_keys,
+				ARRAY_SIZE(xfrm_flow_dissector_keys));
+
 	register_pernet_subsys(&xfrm_net_ops);
 	xfrm_dev_init();
 	xfrm_input_init();