Date:   Thu, 26 May 2022 23:35:00 +0200
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, davem@...emloft.net, kuba@...nel.org,
        edumazet@...gle.com, pabeni@...hat.com, pablo@...filter.org,
        fw@...len.de, netfilter-devel@...r.kernel.org,
        lorenzo.bianconi@...hat.com, brouer@...hat.com, toke@...hat.com,
        memxor@...il.com, yhs@...com
Subject: [PATCH v4 bpf-next 12/14] net: netfilter: add kfunc helpers to alloc and insert a new ct entry

Introduce bpf_xdp_ct_alloc, bpf_skb_ct_alloc and bpf_ct_insert_entry
kfunc helpers in order to add a new entry to ct map from an ebpf program.
Introduce bpf_nf_ct_tuple_parse utility routine.

Acked-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
 net/netfilter/nf_conntrack_bpf.c | 249 ++++++++++++++++++++++++++++---
 1 file changed, 226 insertions(+), 23 deletions(-)

diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c
index c50f4c1e5b3a..70731b57b2d4 100644
--- a/net/netfilter/nf_conntrack_bpf.c
+++ b/net/netfilter/nf_conntrack_bpf.c
@@ -57,41 +57,106 @@ enum {
 	NF_BPF_CT_OPTS_SZ = 12,
 };
 
-static struct nf_conn *__bpf_nf_ct_lookup(struct net *net,
-					  struct bpf_sock_tuple *bpf_tuple,
-					  u32 tuple_len, u8 protonum,
-					  s32 netns_id, u8 *dir)
+static int bpf_nf_ct_tuple_parse(struct bpf_sock_tuple *bpf_tuple,
+				 u32 tuple_len, u8 protonum, u8 dir,
+				 struct nf_conntrack_tuple *tuple)
 {
-	struct nf_conntrack_tuple_hash *hash;
-	struct nf_conntrack_tuple tuple;
-	struct nf_conn *ct;
+	union nf_inet_addr *src = dir ? &tuple->dst.u3 : &tuple->src.u3;
+	union nf_inet_addr *dst = dir ? &tuple->src.u3 : &tuple->dst.u3;
+	union nf_conntrack_man_proto *sport = dir ? (void *)&tuple->dst.u
+						  : &tuple->src.u;
+	union nf_conntrack_man_proto *dport = dir ? &tuple->src.u
+						  : (void *)&tuple->dst.u;
 
 	if (unlikely(protonum != IPPROTO_TCP && protonum != IPPROTO_UDP))
-		return ERR_PTR(-EPROTO);
-	if (unlikely(netns_id < BPF_F_CURRENT_NETNS))
-		return ERR_PTR(-EINVAL);
+		return -EPROTO;
+
+	memset(tuple, 0, sizeof(*tuple));
 
-	memset(&tuple, 0, sizeof(tuple));
 	switch (tuple_len) {
 	case sizeof(bpf_tuple->ipv4):
-		tuple.src.l3num = AF_INET;
-		tuple.src.u3.ip = bpf_tuple->ipv4.saddr;
-		tuple.src.u.tcp.port = bpf_tuple->ipv4.sport;
-		tuple.dst.u3.ip = bpf_tuple->ipv4.daddr;
-		tuple.dst.u.tcp.port = bpf_tuple->ipv4.dport;
+		tuple->src.l3num = AF_INET;
+		src->ip = bpf_tuple->ipv4.saddr;
+		sport->tcp.port = bpf_tuple->ipv4.sport;
+		dst->ip = bpf_tuple->ipv4.daddr;
+		dport->tcp.port = bpf_tuple->ipv4.dport;
 		break;
 	case sizeof(bpf_tuple->ipv6):
-		tuple.src.l3num = AF_INET6;
-		memcpy(tuple.src.u3.ip6, bpf_tuple->ipv6.saddr, sizeof(bpf_tuple->ipv6.saddr));
-		tuple.src.u.tcp.port = bpf_tuple->ipv6.sport;
-		memcpy(tuple.dst.u3.ip6, bpf_tuple->ipv6.daddr, sizeof(bpf_tuple->ipv6.daddr));
-		tuple.dst.u.tcp.port = bpf_tuple->ipv6.dport;
+		tuple->src.l3num = AF_INET6;
+		memcpy(src->ip6, bpf_tuple->ipv6.saddr, sizeof(bpf_tuple->ipv6.saddr));
+		sport->tcp.port = bpf_tuple->ipv6.sport;
+		memcpy(dst->ip6, bpf_tuple->ipv6.daddr, sizeof(bpf_tuple->ipv6.daddr));
+		dport->tcp.port = bpf_tuple->ipv6.dport;
 		break;
 	default:
-		return ERR_PTR(-EAFNOSUPPORT);
+		return -EAFNOSUPPORT;
+	}
+	tuple->dst.protonum = protonum;
+	tuple->dst.dir = dir;
+
+	return 0;
+}
+
+static struct nf_conn *
+__bpf_nf_ct_alloc_entry(struct net *net, struct bpf_sock_tuple *bpf_tuple,
+			u32 tuple_len, u8 protonum, s32 netns_id, u32 timeout)
+{
+	struct nf_conntrack_tuple otuple, rtuple;
+	struct nf_conn *ct;
+	int err;
+
+	if (unlikely(netns_id < BPF_F_CURRENT_NETNS))
+		return ERR_PTR(-EINVAL);
+
+	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, protonum,
+				    IP_CT_DIR_ORIGINAL, &otuple);
+	if (err < 0)
+		return ERR_PTR(err);
+
+	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, protonum,
+				    IP_CT_DIR_REPLY, &rtuple);
+	if (err < 0)
+		return ERR_PTR(err);
+
+	if (netns_id >= 0) {
+		net = get_net_ns_by_id(net, netns_id);
+		if (unlikely(!net))
+			return ERR_PTR(-ENONET);
 	}
 
-	tuple.dst.protonum = protonum;
+	ct = nf_conntrack_alloc(net, &nf_ct_zone_dflt, &otuple, &rtuple,
+				GFP_ATOMIC);
+	if (IS_ERR(ct))
+		goto out;
+
+	memset(&ct->proto, 0, sizeof(ct->proto));
+	ct->timeout = timeout * HZ + jiffies;
+	ct->status |= IPS_CONFIRMED;
+
+out:
+	if (netns_id >= 0)
+		put_net(net);
+
+	return ct;
+}
+
+static struct nf_conn *__bpf_nf_ct_lookup(struct net *net,
+					  struct bpf_sock_tuple *bpf_tuple,
+					  u32 tuple_len, u8 protonum,
+					  s32 netns_id, u8 *dir)
+{
+	struct nf_conntrack_tuple_hash *hash;
+	struct nf_conntrack_tuple tuple;
+	struct nf_conn *ct;
+	int err;
+
+	if (unlikely(netns_id < BPF_F_CURRENT_NETNS))
+		return ERR_PTR(-EINVAL);
+
+	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, protonum,
+				    IP_CT_DIR_ORIGINAL, &tuple);
+	if (err < 0)
+		return ERR_PTR(err);
 
 	if (netns_id >= 0) {
 		net = get_net_ns_by_id(net, netns_id);
@@ -116,6 +181,49 @@ __diag_push();
 __diag_ignore_all("-Wmissing-prototypes",
 		  "Global functions as their definitions will be in nf_conntrack BTF");
 
+/* bpf_xdp_ct_alloc - Alloc a new CT entry for the given tuple
+ *
+ * Parameters:
+ * @xdp_ctx	- Pointer to ctx (xdp_md) in XDP program
+ *		    Cannot be NULL
+ * @bpf_tuple	- Pointer to memory representing the tuple to look up
+ *		    Cannot be NULL
+ * @tuple__sz	- Length of the tuple structure
+ *		    Must be one of sizeof(bpf_tuple->ipv4) or
+ *		    sizeof(bpf_tuple->ipv6)
+ * @opts	- Additional options for lookup (documented above)
+ *		    Cannot be NULL
+ * @opts__sz	- Length of the bpf_ct_opts structure
+ *		    Must be NF_BPF_CT_OPTS_SZ (12)
+ */
+struct nf_conn *
+bpf_xdp_ct_alloc(struct xdp_md *xdp_ctx, struct bpf_sock_tuple *bpf_tuple,
+		 u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
+{
+	struct xdp_buff *ctx = (struct xdp_buff *)xdp_ctx;
+	struct nf_conn *nfct;
+
+	BUILD_BUG_ON(sizeof(struct bpf_ct_opts) != NF_BPF_CT_OPTS_SZ);
+	if (!opts)
+		return NULL;
+
+	if (!bpf_tuple || opts->reserved[0] || opts->reserved[1] ||
+	    opts__sz != NF_BPF_CT_OPTS_SZ) {
+		opts->error = -EINVAL;
+		return NULL;
+	}
+
+	nfct =  __bpf_nf_ct_alloc_entry(dev_net(ctx->rxq->dev), bpf_tuple,
+					tuple__sz, opts->l4proto,
+					opts->netns_id, 10);
+	if (IS_ERR_OR_NULL(nfct)) {
+		opts->error = PTR_ERR(nfct);
+		return NULL;
+	}
+
+	return nfct;
+}
+
 /* bpf_xdp_ct_lookup - Lookup CT entry for the given tuple, and acquire a
  *		       reference to it
  *
@@ -159,6 +267,50 @@ bpf_xdp_ct_lookup(struct xdp_md *xdp_ctx, struct bpf_sock_tuple *bpf_tuple,
 	return nfct;
 }
 
+/* bpf_skb_ct_alloc - Alloc a new CT entry for the given tuple
+ *
+ * Parameters:
+ * @skb_ctx	- Pointer to ctx (__sk_buff) in TC program
+ *		    Cannot be NULL
+ * @bpf_tuple	- Pointer to memory representing the tuple to look up
+ *		    Cannot be NULL
+ * @tuple__sz	- Length of the tuple structure
+ *		    Must be one of sizeof(bpf_tuple->ipv4) or
+ *		    sizeof(bpf_tuple->ipv6)
+ * @opts	- Additional options for lookup (documented above)
+ *		    Cannot be NULL
+ * @opts__sz	- Length of the bpf_ct_opts structure
+ *		    Must be NF_BPF_CT_OPTS_SZ (12)
+ */
+struct nf_conn *
+bpf_skb_ct_alloc(struct __sk_buff *skb_ctx, struct bpf_sock_tuple *bpf_tuple,
+		 u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
+{
+	struct sk_buff *skb = (struct sk_buff *)skb_ctx;
+	struct nf_conn *nfct;
+	struct net *net;
+
+	BUILD_BUG_ON(sizeof(struct bpf_ct_opts) != NF_BPF_CT_OPTS_SZ);
+	if (!opts)
+		return NULL;
+
+	if (!bpf_tuple || opts->reserved[0] || opts->reserved[1] ||
+	    opts__sz != NF_BPF_CT_OPTS_SZ) {
+		opts->error = -EINVAL;
+		return NULL;
+	}
+
+	net = skb->dev ? dev_net(skb->dev) : sock_net(skb->sk);
+	nfct = __bpf_nf_ct_alloc_entry(net, bpf_tuple, tuple__sz,
+				       opts->l4proto, opts->netns_id, 10);
+	if (IS_ERR_OR_NULL(nfct)) {
+		opts->error = PTR_ERR(nfct);
+		return NULL;
+	}
+
+	return nfct;
+}
+
 /* bpf_skb_ct_lookup - Lookup CT entry for the given tuple, and acquire a
  *		       reference to it
  *
@@ -202,6 +354,40 @@ bpf_skb_ct_lookup(struct __sk_buff *skb_ctx, struct bpf_sock_tuple *bpf_tuple,
 	return nfct;
 }
 
+/* bpf_ct_insert_entry - Add the provided entry into a CT map
+ *
+ * This must be invoked for referenced PTR_TO_BTF_ID.
+ *
+ * @nfct__ref	 - Pointer to referenced nf_conn object
+ */
+const struct nf_conn *
+bpf_ct_insert_entry(struct nf_conn *nfct__ref, struct bpf_ct_opts *opts,
+		    u32 opts__sz)
+{
+	int err;
+
+	BUILD_BUG_ON(sizeof(struct bpf_ct_opts) != NF_BPF_CT_OPTS_SZ);
+
+	if (!nfct__ref)
+		return NULL;
+
+	if (!opts || opts->reserved[0] || opts->reserved[1] ||
+	    opts__sz != NF_BPF_CT_OPTS_SZ) {
+		nf_conntrack_free(nfct__ref);
+		opts->error = -EINVAL;
+		return NULL;
+	}
+
+	err = nf_conntrack_hash_check_insert(nfct__ref);
+	if (err < 0) {
+		nf_conntrack_free(nfct__ref);
+		opts->error = err;
+		return NULL;
+	}
+
+	return nfct__ref;
+}
+
 /* bpf_ct_release - Release acquired nf_conn object
  *
  * This must be invoked for referenced PTR_TO_BTF_ID, and the verifier rejects
@@ -243,23 +429,31 @@ void bpf_ct_refresh_timeout(const struct nf_conn *nfct__ref, u32 timeout)
 __diag_pop()
 
 BTF_SET_START(nf_ct_xdp_check_kfunc_ids)
+BTF_ID(func, bpf_xdp_ct_alloc)
 BTF_ID(func, bpf_xdp_ct_lookup)
+BTF_ID(func, bpf_ct_insert_entry)
 BTF_ID(func, bpf_ct_release)
 BTF_ID(func, bpf_ct_refresh_timeout);
 BTF_SET_END(nf_ct_xdp_check_kfunc_ids)
 
 BTF_SET_START(nf_ct_tc_check_kfunc_ids)
+BTF_ID(func, bpf_skb_ct_alloc)
 BTF_ID(func, bpf_skb_ct_lookup)
+BTF_ID(func, bpf_ct_insert_entry)
 BTF_ID(func, bpf_ct_release)
 BTF_ID(func, bpf_ct_refresh_timeout);
 BTF_SET_END(nf_ct_tc_check_kfunc_ids)
 
 BTF_SET_START(nf_ct_acquire_kfunc_ids)
+BTF_ID(func, bpf_xdp_ct_alloc)
 BTF_ID(func, bpf_xdp_ct_lookup)
+BTF_ID(func, bpf_skb_ct_alloc)
 BTF_ID(func, bpf_skb_ct_lookup)
+BTF_ID(func, bpf_ct_insert_entry)
 BTF_SET_END(nf_ct_acquire_kfunc_ids)
 
 BTF_SET_START(nf_ct_release_kfunc_ids)
+BTF_ID(func, bpf_ct_insert_entry)
 BTF_ID(func, bpf_ct_release)
 BTF_SET_END(nf_ct_release_kfunc_ids)
 
@@ -267,12 +461,21 @@ BTF_SET_END(nf_ct_release_kfunc_ids)
 #define nf_ct_ret_null_kfunc_ids nf_ct_acquire_kfunc_ids
 
 BTF_ID_LIST(nf_ct_acq_rel_pairs)
+BTF_ID(func, bpf_xdp_ct_alloc)
+BTF_ID(func, bpf_ct_insert_entry)
+
+BTF_ID(func, bpf_skb_ct_alloc)
+BTF_ID(func, bpf_ct_insert_entry)
+
 BTF_ID(func, bpf_xdp_ct_lookup)
 BTF_ID(func, bpf_ct_release)
 
 BTF_ID(func, bpf_skb_ct_lookup)
 BTF_ID(func, bpf_ct_release)
 
+BTF_ID(func, bpf_ct_insert_entry)
+BTF_ID(func, bpf_ct_release)
+
 static const struct btf_kfunc_id_set nf_conntrack_xdp_kfunc_set = {
 	.owner             = THIS_MODULE,
 	.check_set         = &nf_ct_xdp_check_kfunc_ids,
-- 
2.35.3

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