[PATCH nf-next,v4] netfilter: flowtable: initial bridge support

This patch adds bridge flowtable support, this allows to define a
shortcut between two bridge ports. This is complementary to the
existing inet family flowtable support.

Set up does not require userspace updates, an example ruleset to
enable the flowtable in the bridge family is provided here below:

 table bridge x {
        flowtable y {
                hook ingress priority 0
                devices = { veth0, veth1 }
        }
        chain forward {
                type filter hook forward priority 0
                ip protocol tcp flow add @y counter
                counter
        }
 }

I decided to add an explicit nft_flow_offload_bridge_eval() instead of
recycling the existing inet function by adding branches to skip the
routing part which is obviously not needed in the bridge path. I
consider this mostly boiler plate for feature extensibility and better
maintability is better to keep it separated. Similarly, the bridge hook
that represents the flowtable bridge datapath is implemented in a
separated function.

Although connection tracking in the bridge does not support the tracking
of IP flows encapsulated in PPPoE and VLAN tracking yet, there are
scenarios that involved PPPoE and VLAN that can be supported already,
such as those where packets flows through the bridge with no tagging,
eg. a VLAN device is used as a bridge port which decapsulates the
packets at the ingress path.

Tested with:
- Plain forwarding between bridge ports with no VLAN tagging.
- VLAN device used in bridged ports, as long as packets that are
  untagged when circulating within the bridge.

This initial bridge flowtable support does support VLAN tagged packets
circulating within the bridge yet, because nf_conntrack_bridge still
does not support PPPoE/VLAN natively.

Source and destination mac addresses are statically cached in the flow
tuple Roaming between devices is not supported either.

No hardware offload at this stage, but patches has been proposed to
enable it and will follow up.

Signed-off-by: Pablo Neira Ayuso <[email protected]>
---
v4: - is_skb_forwardable() is missing VLAN_HLEN in the check, add by
      now a custom similar to nf_flow_exceeds_mtu(), explore consolidation
      later on with core infrastructure if possible.
    - Skip packets if nf_bridge_info_exists() returns true, this does not
      support the br_netfilter layer that mocks the IP layer for the bridge.

 include/net/netfilter/nf_flow_table.h |   7 ++
 net/netfilter/nf_flow_table_inet.c    |  12 ++
 net/netfilter/nf_flow_table_ip.c      | 154 ++++++++++++++++++++++++++
 net/netfilter/nf_flow_table_offload.c |   8 +-
 net/netfilter/nf_flow_table_path.c    |  63 +++++++++++
 net/netfilter/nft_flow_offload.c      |  96 +++++++++++++++-
 6 files changed, 336 insertions(+), 4 deletions(-)

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index ce414118962f..6e76a6879ff3 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -248,6 +248,8 @@ struct nft_pktinfo;
 int nft_flow_route(const struct nft_pktinfo *pkt, const struct nf_conn *ct,
 		   struct nf_flow_route *route, enum ip_conntrack_dir dir,
 		   struct nft_flowtable *ft);
+int nft_flow_bridge(struct flow_offload *flow, const struct nft_pktinfo *pkt,
+		    enum ip_conntrack_dir dir, struct nft_flowtable *ft);
 
 static inline int
 nf_flow_table_offload_add_cb(struct nf_flowtable *flow_table,
@@ -342,6 +344,8 @@ unsigned int nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 				     const struct nf_hook_state *state);
 unsigned int nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 				       const struct nf_hook_state *state);
+unsigned int nf_flow_offload_bridge_hook(void *priv, struct sk_buff *skb,
+					 const struct nf_hook_state *state);
 
 #if (IS_BUILTIN(CONFIG_NF_FLOW_TABLE) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) || \
     (IS_MODULE(CONFIG_NF_FLOW_TABLE) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES))
@@ -377,6 +381,9 @@ int nf_flow_rule_route_ipv4(struct net *net, struct flow_offload *flow,
 int nf_flow_rule_route_ipv6(struct net *net, struct flow_offload *flow,
 			    enum flow_offload_tuple_dir dir,
 			    struct nf_flow_rule *flow_rule);
+int nf_flow_rule_bridge(struct net *net, struct flow_offload *flow,
+			enum flow_offload_tuple_dir dir,
+			struct nf_flow_rule *flow_rule);
 
 int nf_flow_table_offload_init(void);
 void nf_flow_table_offload_exit(void);
diff --git a/net/netfilter/nf_flow_table_inet.c b/net/netfilter/nf_flow_table_inet.c
index b0f199171932..44790a0d3012 100644
--- a/net/netfilter/nf_flow_table_inet.c
+++ b/net/netfilter/nf_flow_table_inet.c
@@ -65,6 +65,15 @@ static int nf_flow_rule_route_inet(struct net *net,
 	return err;
 }
 
+static struct nf_flowtable_type flowtable_bridge = {
+	.family		= NFPROTO_BRIDGE,
+	.init		= nf_flow_table_init,
+	.setup		= nf_flow_table_offload_setup,
+	.free		= nf_flow_table_free,
+	.hook		= nf_flow_offload_bridge_hook,
+	.owner		= THIS_MODULE,
+};
+
 static struct nf_flowtable_type flowtable_inet = {
 	.family		= NFPROTO_INET,
 	.init		= nf_flow_table_init,
@@ -97,6 +106,7 @@ static struct nf_flowtable_type flowtable_ipv6 = {
 
 static int __init nf_flow_inet_module_init(void)
 {
+	nft_register_flowtable_type(&flowtable_bridge);
 	nft_register_flowtable_type(&flowtable_ipv4);
 	nft_register_flowtable_type(&flowtable_ipv6);
 	nft_register_flowtable_type(&flowtable_inet);
@@ -109,6 +119,7 @@ static void __exit nf_flow_inet_module_exit(void)
 	nft_unregister_flowtable_type(&flowtable_inet);
 	nft_unregister_flowtable_type(&flowtable_ipv6);
 	nft_unregister_flowtable_type(&flowtable_ipv4);
+	nft_unregister_flowtable_type(&flowtable_bridge);
 }
 
 module_init(nf_flow_inet_module_init);
@@ -118,5 +129,6 @@ MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Pablo Neira Ayuso <[email protected]>");
 MODULE_ALIAS_NF_FLOWTABLE(AF_INET);
 MODULE_ALIAS_NF_FLOWTABLE(AF_INET6);
+MODULE_ALIAS_NF_FLOWTABLE(AF_BRIDGE);
 MODULE_ALIAS_NF_FLOWTABLE(1); /* NFPROTO_INET */
 MODULE_DESCRIPTION("Netfilter flow table mixed IPv4/IPv6 module");
diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
index 0b78decce8a9..1c8ef6e9c680 100644
--- a/net/netfilter/nf_flow_table_ip.c
+++ b/net/netfilter/nf_flow_table_ip.c
@@ -1199,3 +1199,157 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 	return nf_flow_queue_xmit(state->net, skb, &xmit);
 }
 EXPORT_SYMBOL_GPL(nf_flow_offload_ipv6_hook);
+
+/* Based on is_skb_forwardable(), including ETH_HLEN. */
+static bool nft_br_is_skb_forwardable(const struct net_device *dev,
+				      const struct sk_buff *skb)
+{
+	const u32 vlan_hdr_len = VLAN_HLEN;
+	unsigned int len;
+
+	if (!(dev->flags & IFF_UP))
+		return false;
+
+	len = dev->mtu + dev->hard_header_len + vlan_hdr_len + ETH_HLEN;
+	if (skb->len <= len || skb_is_gso(skb))
+		return true;
+
+	return false;
+}
+
+static int nf_flow_bridge_xmit(struct net *net,
+			       struct nf_flowtable *flow_table,
+			       struct flow_offload *flow,
+			       enum flow_offload_tuple_dir dir,
+			       struct sk_buff *skb)
+{
+	struct flow_offload_tuple *other_tuple = &flow->tuplehash[!dir].tuple;
+	struct flow_offload_tuple *this_tuple = &flow->tuplehash[dir].tuple;
+	struct nf_flow_xmit xmit = {};
+
+	xmit.outdev = dev_get_by_index_rcu(net, this_tuple->out.ifidx);
+	if (!xmit.outdev) {
+		flow_offload_teardown(flow);
+		return NF_DROP;
+	}
+
+	if (!nft_br_is_skb_forwardable(xmit.outdev, skb))
+		return NF_DROP;
+
+	if (flow_table->flags & NF_FLOWTABLE_COUNTER)
+		nf_ct_acct_update(flow->ct, dir, skb->len);
+
+	xmit.dest = this_tuple->out.h_dest;
+	xmit.source = this_tuple->out.h_source;
+	xmit.tuple = other_tuple;
+	xmit.needs_gso_segment = this_tuple->needs_gso_segment;
+
+	return nf_flow_queue_xmit(net, skb, &xmit);
+}
+
+static unsigned int
+nf_flow_offload_ip_bridge(void *priv, struct sk_buff *skb,
+			  const struct nf_hook_state *state)
+{
+	struct flow_offload_tuple_rhash *tuplehash;
+	struct nf_flowtable *flow_table = priv;
+	enum flow_offload_tuple_dir dir;
+	struct nf_flowtable_ctx ctx = {
+		.in	= state->in,
+	};
+	struct flow_offload *flow;
+	unsigned int thoff;
+	struct iphdr *iph;
+
+	tuplehash = nf_flow_offload_lookup(&ctx, flow_table, skb);
+	if (!tuplehash)
+		return NF_ACCEPT;
+
+	dir = tuplehash->tuple.dir;
+	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
+
+	iph = (struct iphdr *)(skb_network_header(skb) + ctx.offset);
+	thoff = (iph->ihl * 4) + ctx.offset;
+	if (nf_flow_state_check(flow, iph->protocol, skb, thoff))
+		return NF_ACCEPT;
+
+	if (skb_ensure_writable(skb, thoff + ctx.hdrsize))
+		return NF_DROP;
+
+	flow_offload_refresh(flow_table, flow, false);
+	nf_flow_encap_pop(&ctx, skb, tuplehash);
+	skb_clear_tstamp(skb);
+
+	return nf_flow_bridge_xmit(state->net, flow_table, flow, dir, skb);
+}
+
+static unsigned int
+nf_flow_offload_ipv6_bridge(void *priv, struct sk_buff *skb,
+			    const struct nf_hook_state *state)
+{
+	struct flow_offload_tuple_rhash *tuplehash;
+	struct nf_flowtable *flow_table = priv;
+	enum flow_offload_tuple_dir dir;
+	struct nf_flowtable_ctx ctx = {
+		.in	= state->in,
+	};
+	struct flow_offload *flow;
+	struct ipv6hdr *ip6h;
+	unsigned int thoff;
+
+	tuplehash = nf_flow_offload_ipv6_lookup(&ctx, flow_table, skb);
+	if (!tuplehash)
+		return NF_ACCEPT;
+
+	dir = tuplehash->tuple.dir;
+	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
+
+	ip6h = (struct ipv6hdr *)(skb_network_header(skb) + ctx.offset);
+	thoff = sizeof(*ip6h) + ctx.offset;
+	if (nf_flow_state_check(flow, ip6h->nexthdr, skb, thoff))
+		return NF_ACCEPT;
+
+	if (skb_ensure_writable(skb, thoff + ctx.hdrsize))
+		return NF_DROP;
+
+	flow_offload_refresh(flow_table, flow, false);
+	nf_flow_encap_pop(&ctx, skb, tuplehash);
+	skb_clear_tstamp(skb);
+
+	return nf_flow_bridge_xmit(state->net, flow_table, flow, dir, skb);
+}
+
+unsigned int
+nf_flow_offload_bridge_hook(void *priv, struct sk_buff *skb,
+			    const struct nf_hook_state *state)
+{
+	struct vlan_ethhdr *veth;
+	__be16 proto;
+
+	switch (skb->protocol) {
+	case htons(ETH_P_8021Q):
+		if (!pskb_may_pull(skb, skb_mac_offset(skb) + sizeof(*veth)))
+			return NF_ACCEPT;
+
+		veth = (struct vlan_ethhdr *)skb_mac_header(skb);
+		proto = veth->h_vlan_encapsulated_proto;
+		break;
+	case htons(ETH_P_PPP_SES):
+		if (!nf_flow_pppoe_proto(skb, &proto))
+			return NF_ACCEPT;
+		break;
+	default:
+		proto = skb->protocol;
+		break;
+	}
+
+	switch (proto) {
+	case htons(ETH_P_IP):
+		return nf_flow_offload_ip_bridge(priv, skb, state);
+	case htons(ETH_P_IPV6):
+		return nf_flow_offload_ipv6_bridge(priv, skb, state);
+	}
+
+	return NF_ACCEPT;
+}
+EXPORT_SYMBOL_GPL(nf_flow_offload_bridge_hook);
diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index 801a3dd9ceea..cd8d468fe0c9 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -1101,9 +1101,11 @@ nf_flow_offload_work_alloc(struct nf_flowtable *flowtable,
 	return offload;
 }
 
-static bool nf_flow_offload_unsupported(struct flow_offload *flow)
+static bool nf_flow_offload_unsupported(struct nf_flowtable *flowtable,
+					struct flow_offload *flow)
 {
-	if (flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.tun_num ||
+	if (flowtable->type->family == NFPROTO_BRIDGE ||
+	    flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.tun_num ||
 	    flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.tun_num)
 		return true;
 
@@ -1125,7 +1127,7 @@ void nf_flow_offload_refresh(struct nf_flowtable *flowtable,
 void nf_flow_offload_add(struct nf_flowtable *flowtable,
 			 struct flow_offload *flow)
 {
-	if (nf_flow_offload_unsupported(flow))
+	if (nf_flow_offload_unsupported(flowtable, flow))
 		return;
 
 	set_bit(NF_FLOW_HW, &flow->flags);
diff --git a/net/netfilter/nf_flow_table_path.c b/net/netfilter/nf_flow_table_path.c
index 98c03b487f52..288d687b6b92 100644
--- a/net/netfilter/nf_flow_table_path.c
+++ b/net/netfilter/nf_flow_table_path.c
@@ -8,6 +8,7 @@
 #include <linux/spinlock.h>
 #include <linux/netfilter/nf_conntrack_common.h>
 #include <linux/netfilter/nf_tables.h>
+#include <linux/if_vlan.h>
 #include <net/ip.h>
 #include <net/inet_dscp.h>
 #include <net/netfilter/nf_tables.h>
@@ -350,3 +351,65 @@ int nft_flow_route(const struct nft_pktinfo *pkt, const struct nf_conn *ct,
 	return -ENOENT;
 }
 EXPORT_SYMBOL_GPL(nft_flow_route);
+
+static int nft_dev_fill_bridge_path(struct flow_offload *flow,
+				    struct nft_flowtable *ft,
+				    enum ip_conntrack_dir dir,
+				    const struct net_device *dev,
+				    unsigned char *src_ha,
+				    unsigned char *dst_ha)
+{
+	struct flow_offload_tuple *this_tuple = &flow->tuplehash[dir].tuple;
+	struct net_device_path_stack stack;
+	struct nft_forward_info info = {};
+	int i, j = 0;
+
+	if (dev_fill_forward_path(dev, dst_ha, &stack) < 0 ||
+	    nft_dev_path_info(&stack, &info, dst_ha, &ft->data) < 0)
+		return -1;
+
+	if (!nft_flowtable_find_dev(info.indev, ft))
+		return -1;
+
+	this_tuple->iifidx = info.indev->ifindex;
+	for (i = info.num_encaps - 1; i >= 0; i--) {
+		this_tuple->encap[j].id = info.encap[i].id;
+		this_tuple->encap[j].proto = info.encap[i].proto;
+		j++;
+	}
+	this_tuple->encap_num = info.num_encaps;
+
+	ether_addr_copy(this_tuple->out.h_source, src_ha);
+	ether_addr_copy(this_tuple->out.h_dest, dst_ha);
+	this_tuple->needs_gso_segment = info.needs_gso_segment;
+	this_tuple->xmit_type = FLOW_OFFLOAD_XMIT_DIRECT;
+
+	return 0;
+}
+
+int nft_flow_bridge(struct flow_offload *flow, const struct nft_pktinfo *pkt,
+		    enum ip_conntrack_dir dir, struct nft_flowtable *ft)
+{
+	struct flow_offload_tuple *other_tuple = &flow->tuplehash[!dir].tuple;
+	struct flow_offload_tuple *this_tuple = &flow->tuplehash[dir].tuple;
+	const struct net_device *outdev = nft_out(pkt);
+	const struct net_device *indev = nft_in(pkt);
+	struct ethhdr *eth = eth_hdr(pkt->skb);
+	int err;
+
+	err = nft_dev_fill_bridge_path(flow, ft, dir, indev,
+				       eth->h_source, eth->h_dest);
+	if (err < 0)
+		return err;
+
+	err = nft_dev_fill_bridge_path(flow, ft, !dir, outdev,
+				       eth->h_dest, eth->h_source);
+	if (err < 0)
+		return err;
+
+	this_tuple->out.ifidx = other_tuple->iifidx;
+	other_tuple->out.ifidx = this_tuple->iifidx;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nft_flow_bridge);
diff --git a/net/netfilter/nft_flow_offload.c b/net/netfilter/nft_flow_offload.c
index 32b4281038dd..6e3ca1d82d15 100644
--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c
@@ -9,6 +9,7 @@
 #include <linux/spinlock.h>
 #include <linux/netfilter/nf_conntrack_common.h>
 #include <linux/netfilter/nf_tables.h>
+#include <linux/netfilter_bridge.h>
 #include <net/ip.h>
 #include <net/flow.h>
 #include <net/netfilter/nf_tables.h>
@@ -135,6 +136,70 @@ static void nft_flow_offload_eval(const struct nft_expr *expr,
 	regs->verdict.code = NFT_BREAK;
 }
 
+static void nft_flow_offload_bridge_eval(const struct nft_expr *expr,
+					 struct nft_regs *regs,
+					 const struct nft_pktinfo *pkt)
+{
+	struct nft_flow_offload *priv = nft_expr_priv(expr);
+	struct nf_flowtable *flowtable = &priv->flowtable->data;
+	struct tcphdr _tcph, *tcph = NULL;
+	enum ip_conntrack_info ctinfo;
+	struct flow_offload *flow;
+	enum ip_conntrack_dir dir;
+	struct nf_conn *ct;
+	int ret;
+
+	/* Is this a non-IP packet or br_netfilter? If so, skip. */
+	if (!pkt->flags || nf_bridge_info_exists(pkt->skb))
+		goto out;
+
+	ct = nf_ct_get(pkt->skb, &ctinfo);
+	if (!ct || !nf_ct_is_confirmed(ct))
+		goto out;
+
+	switch (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum) {
+	case IPPROTO_TCP:
+		tcph = skb_header_pointer(pkt->skb, nft_thoff(pkt),
+					  sizeof(_tcph), &_tcph);
+		if (unlikely(!tcph || tcph->fin || tcph->rst ||
+			     !nf_conntrack_tcp_established(ct)))
+			goto out;
+		break;
+	case IPPROTO_UDP:
+		break;
+	default:
+		goto out;
+	}
+
+	if (test_and_set_bit(IPS_OFFLOAD_BIT, &ct->status))
+		goto out;
+
+	flow = flow_offload_alloc(ct);
+	if (!flow)
+		goto err_flow_forward;
+
+	dir = CTINFO2DIR(ctinfo);
+	if (nft_flow_bridge(flow, pkt, dir, priv->flowtable) < 0)
+		goto err_flow_add;
+
+	if (tcph)
+		flow_offload_ct_tcp(ct);
+
+	__set_bit(NF_FLOW_HW_BIDIRECTIONAL, &flow->flags);
+	ret = flow_offload_add(flowtable, flow);
+	if (ret < 0)
+		goto err_flow_add;
+
+	return;
+
+err_flow_add:
+	flow_offload_free(flow);
+err_flow_forward:
+	clear_bit(IPS_OFFLOAD_BIT, &ct->status);
+out:
+	regs->verdict.code = NFT_BREAK;
+}
+
 static int nft_flow_offload_validate(const struct nft_ctx *ctx,
 				     const struct nft_expr *expr)
 {
@@ -142,7 +207,8 @@ static int nft_flow_offload_validate(const struct nft_ctx *ctx,
 
 	if (ctx->family != NFPROTO_IPV4 &&
 	    ctx->family != NFPROTO_IPV6 &&
-	    ctx->family != NFPROTO_INET)
+	    ctx->family != NFPROTO_INET &&
+	    ctx->family != NFPROTO_BRIDGE)
 		return -EOPNOTSUPP;
 
 	return nft_chain_validate_hooks(ctx->chain, hook_mask);
@@ -235,6 +301,27 @@ static struct nft_expr_type nft_flow_offload_type __read_mostly = {
 	.owner		= THIS_MODULE,
 };
 
+static const struct nft_expr_ops nft_flow_offload_bridge_ops = {
+	.type		= &nft_flow_offload_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_flow_offload)),
+	.eval		= nft_flow_offload_bridge_eval,
+	.init		= nft_flow_offload_init,
+	.activate	= nft_flow_offload_activate,
+	.deactivate	= nft_flow_offload_deactivate,
+	.destroy	= nft_flow_offload_destroy,
+	.validate	= nft_flow_offload_validate,
+	.dump		= nft_flow_offload_dump,
+};
+
+static struct nft_expr_type nft_flow_offload_bridge_type __read_mostly = {
+	.name		= "flow_offload",
+	.family		= NFPROTO_BRIDGE,
+	.ops		= &nft_flow_offload_bridge_ops,
+	.policy		= nft_flow_offload_policy,
+	.maxattr	= NFTA_FLOW_MAX,
+	.owner		= THIS_MODULE,
+};
+
 static int flow_offload_netdev_event(struct notifier_block *this,
 				     unsigned long event, void *ptr)
 {
@@ -264,8 +351,14 @@ static int __init nft_flow_offload_module_init(void)
 	if (err < 0)
 		goto register_expr;
 
+	err = nft_register_expr(&nft_flow_offload_bridge_type);
+	if (err < 0)
+		goto register_bridge_expr;
+
 	return 0;
 
+register_bridge_expr:
+	nft_unregister_expr(&nft_flow_offload_type);
 register_expr:
 	unregister_netdevice_notifier(&flow_offload_netdev_notifier);
 err:
@@ -274,6 +367,7 @@ static int __init nft_flow_offload_module_init(void)
 
 static void __exit nft_flow_offload_module_exit(void)
 {
+	nft_unregister_expr(&nft_flow_offload_bridge_type);
 	nft_unregister_expr(&nft_flow_offload_type);
 	unregister_netdevice_notifier(&flow_offload_netdev_notifier);
 }
-- 
2.47.3