netfilter: nf_tables: add support for native socket matching

Now it can only match the transparent flag of an ip/ipv6 socket.

Signed-off-by: Máté Eckl <ecklm94@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 178 insertions, 0 deletions

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 9c71f024f9cc..3d46c82a5ebd 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -905,6 +905,31 @@ enum nft_rt_attributes {
 #define NFTA_RT_MAX             (__NFTA_RT_MAX - 1)
 
 /**
+ * enum nft_socket_attributes - nf_tables socket expression netlink attributes
+ *
+ * @NFTA_SOCKET_KEY: socket key to match
+ * @NFTA_SOCKET_DREG: destination register
+ */
+enum nft_socket_attributes {
+        NFTA_SOCKET_UNSPEC,
+        NFTA_SOCKET_KEY,
+        NFTA_SOCKET_DREG,
+        __NFTA_SOCKET_MAX
+};
+#define NFTA_SOCKET_MAX         (__NFTA_SOCKET_MAX - 1)
+
+/*
+ * enum nft_socket_keys - nf_tables socket expression keys
+ *
+ * @NFT_SOCKET_TRANSPARENT: Value of the IP(V6)_TRANSPARENT socket option_
+ */
+enum nft_socket_keys {
+        NFT_SOCKET_TRANSPARENT,
+        __NFT_SOCKET_MAX
+};
+#define NFT_SOCKET_MAX  (__NFT_SOCKET_MAX - 1)
+
+/**
  * enum nft_ct_keys - nf_tables ct expression keys
  *
  * @NFT_CT_STATE: conntrack state (bitmask of enum ip_conntrack_info)
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 3ec8886850b2..276e1e32f44e 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -613,6 +613,15 @@ config NFT_FIB_INET
           The lookup will be delegated to the IPv4 or IPv6 FIB depending
           on the protocol of the packet.
 
+config NFT_SOCKET
+        tristate "Netfilter nf_tables socket match support"
+        depends on IPV6 || IPV6=n
+        select NF_SOCKET_IPV4
+        select NF_SOCKET_IPV6 if IPV6
+        help
+          This option allows matching for the presence or absence of a
+          corresponding socket and its attributes.
+
 if NF_TABLES_NETDEV
 
 config NF_DUP_NETDEV
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 9b3434360d49..eec169555731 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -102,6 +102,7 @@ obj-$(CONFIG_NFT_FIB)		+= nft_fib.o
 obj-$(CONFIG_NFT_FIB_INET)      += nft_fib_inet.o
 obj-$(CONFIG_NFT_FIB_NETDEV)    += nft_fib_netdev.o
 obj-$(CONFIG_NF_OSF)            += nf_osf.o
+obj-$(CONFIG_NFT_SOCKET)        += nft_socket.o
 
 # nf_tables netdev
 obj-$(CONFIG_NFT_DUP_NETDEV)    += nft_dup_netdev.o
diff --git a/net/netfilter/nft_socket.c b/net/netfilter/nft_socket.c
new file mode 100644
index 000000000000..d86337068ecb
--- /dev/null
+++ b/net/netfilter/nft_socket.c
@@ -0,0 +1,143 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/module.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables_core.h>
+#include <net/netfilter/nf_socket.h>
+#include <net/inet_sock.h>
+
+struct nft_socket {
+        enum nft_socket_keys            key:8;
+        union {
+                enum nft_registers      dreg:8;
+        };
+};
+
+static void nft_socket_eval(const struct nft_expr *expr,
+                            struct nft_regs *regs,
+                            const struct nft_pktinfo *pkt)
+{
+        const struct nft_socket *priv = nft_expr_priv(expr);
+        struct sk_buff *skb = pkt->skb;
+        struct sock *sk = skb->sk;
+        u32 *dest = &regs->data[priv->dreg];
+
+        if (!sk)
+                switch(nft_pf(pkt)) {
+                case NFPROTO_IPV4:
+                        sk = nf_sk_lookup_slow_v4(nft_net(pkt), skb, nft_in(pkt));
+                        break;
+#if IS_ENABLED(CONFIG_NF_SOCKET_IPV6)
+                case NFPROTO_IPV6:
+                        sk = nf_sk_lookup_slow_v6(nft_net(pkt), skb, nft_in(pkt));
+                        break;
+#endif
+                default:
+                        WARN_ON_ONCE(1);
+                        regs->verdict.code = NFT_BREAK;
+                        return;
+                }
+
+        if(!sk) {
+                nft_reg_store8(dest, 0);
+                return;
+        }
+
+        /* So that subsequent socket matching not to require other lookups. */
+        skb->sk = sk;
+
+        switch(priv->key) {
+        case NFT_SOCKET_TRANSPARENT:
+                nft_reg_store8(dest, nf_sk_is_transparent(sk));
+                break;
+        default:
+                WARN_ON(1);
+                regs->verdict.code = NFT_BREAK;
+        }
+}
+
+static const struct nla_policy nft_socket_policy[NFTA_SOCKET_MAX + 1] = {
+        [NFTA_SOCKET_KEY]               = { .type = NLA_U32 },
+        [NFTA_SOCKET_DREG]              = { .type = NLA_U32 },
+};
+
+static int nft_socket_init(const struct nft_ctx *ctx,
+                           const struct nft_expr *expr,
+                           const struct nlattr * const tb[])
+{
+        struct nft_socket *priv = nft_expr_priv(expr);
+        unsigned int len;
+
+        if (!tb[NFTA_SOCKET_DREG] || !tb[NFTA_SOCKET_KEY])
+                return -EINVAL;
+
+        switch(ctx->family) {
+        case NFPROTO_IPV4:
+#if IS_ENABLED(CONFIG_NF_SOCKET_IPV6)
+        case NFPROTO_IPV6:
+#endif
+        case NFPROTO_INET:
+                break;
+        default:
+                return -EOPNOTSUPP;
+        }
+
+        priv->key = ntohl(nla_get_u32(tb[NFTA_SOCKET_KEY]));
+        switch(priv->key) {
+        case NFT_SOCKET_TRANSPARENT:
+                len = sizeof(u8);
+                break;
+        default:
+                return -EOPNOTSUPP;
+        }
+
+        priv->dreg = nft_parse_register(tb[NFTA_SOCKET_DREG]);
+        return nft_validate_register_store(ctx, priv->dreg, NULL,
+                                           NFT_DATA_VALUE, len);
+}
+
+static int nft_socket_dump(struct sk_buff *skb,
+                           const struct nft_expr *expr)
+{
+        const struct nft_socket *priv = nft_expr_priv(expr);
+
+        if (nla_put_u32(skb, NFTA_SOCKET_KEY, htonl(priv->key)))
+                return -1;
+        if (nft_dump_register(skb, NFTA_SOCKET_DREG, priv->dreg))
+                return -1;
+        return 0;
+}
+
+static struct nft_expr_type nft_socket_type;
+static const struct nft_expr_ops nft_socket_ops = {
+        .type           = &nft_socket_type,
+        .size           = NFT_EXPR_SIZE(sizeof(struct nft_socket)),
+        .eval           = nft_socket_eval,
+        .init           = nft_socket_init,
+        .dump           = nft_socket_dump,
+};
+
+static struct nft_expr_type nft_socket_type __read_mostly = {
+        .name           = "socket",
+        .ops            = &nft_socket_ops,
+        .policy         = nft_socket_policy,
+        .maxattr        = NFTA_SOCKET_MAX,
+        .owner          = THIS_MODULE,
+};
+
+static int __init nft_socket_module_init(void)
+{
+        return nft_register_expr(&nft_socket_type);
+}
+
+static void __exit nft_socket_module_exit(void)
+{
+        nft_unregister_expr(&nft_socket_type);
+}
+
+module_init(nft_socket_module_init);
+module_exit(nft_socket_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Máté Eckl");
+MODULE_DESCRIPTION("nf_tables socket match module");