--- /dev/null
+/* 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_tproxy.h>
+#include <net/inet_sock.h>
+#include <net/tcp.h>
+#include <linux/if_ether.h>
+#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
+#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
+#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
+#endif
+
+struct nft_tproxy {
+ enum nft_registers sreg_addr:8;
+ enum nft_registers sreg_port:8;
+ u8 family;
+};
+
+static void nft_tproxy_eval_v4(const struct nft_expr *expr,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ const struct nft_tproxy *priv = nft_expr_priv(expr);
+ struct sk_buff *skb = pkt->skb;
+ const struct iphdr *iph = ip_hdr(skb);
+ struct udphdr _hdr, *hp;
+ __be32 taddr = 0;
+ __be16 tport = 0;
+ struct sock *sk;
+
+ hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
+ if (!hp) {
+ regs->verdict.code = NFT_BREAK;
+ return;
+ }
+
+ /* check if there's an ongoing connection on the packet addresses, this
+ * happens if the redirect already happened and the current packet
+ * belongs to an already established connection
+ */
+ sk = nf_tproxy_get_sock_v4(nft_net(pkt), skb, iph->protocol,
+ iph->saddr, iph->daddr,
+ hp->source, hp->dest,
+ skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED);
+
+ if (priv->sreg_addr)
+ taddr = regs->data[priv->sreg_addr];
+ taddr = nf_tproxy_laddr4(skb, taddr, iph->daddr);
+
+ if (priv->sreg_port)
+ tport = regs->data[priv->sreg_port];
+ if (!tport)
+ tport = hp->dest;
+
+ /* UDP has no TCP_TIME_WAIT state, so we never enter here */
+ if (sk && sk->sk_state == TCP_TIME_WAIT) {
+ /* reopening a TIME_WAIT connection needs special handling */
+ sk = nf_tproxy_handle_time_wait4(nft_net(pkt), skb, taddr, tport, sk);
+ } else if (!sk) {
+ /* no, there's no established connection, check if
+ * there's a listener on the redirected addr/port
+ */
+ sk = nf_tproxy_get_sock_v4(nft_net(pkt), skb, iph->protocol,
+ iph->saddr, taddr,
+ hp->source, tport,
+ skb->dev, NF_TPROXY_LOOKUP_LISTENER);
+ }
+
+ if (sk && nf_tproxy_sk_is_transparent(sk))
+ nf_tproxy_assign_sock(skb, sk);
+ else
+ regs->verdict.code = NFT_BREAK;
+}
+
+#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
+static void nft_tproxy_eval_v6(const struct nft_expr *expr,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ const struct nft_tproxy *priv = nft_expr_priv(expr);
+ struct sk_buff *skb = pkt->skb;
+ const struct ipv6hdr *iph = ipv6_hdr(skb);
+ struct in6_addr taddr = {0};
+ int thoff = pkt->xt.thoff;
+ struct udphdr _hdr, *hp;
+ __be16 tport = 0;
+ struct sock *sk;
+ int l4proto;
+
+ if (!pkt->tprot_set) {
+ regs->verdict.code = NFT_BREAK;
+ return;
+ }
+ l4proto = pkt->tprot;
+
+ hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
+ if (hp == NULL) {
+ regs->verdict.code = NFT_BREAK;
+ return;
+ }
+
+ /* check if there's an ongoing connection on the packet addresses, this
+ * happens if the redirect already happened and the current packet
+ * belongs to an already established connection
+ */
+ sk = nf_tproxy_get_sock_v6(nft_net(pkt), skb, thoff, l4proto,
+ &iph->saddr, &iph->daddr,
+ hp->source, hp->dest,
+ nft_in(pkt), NF_TPROXY_LOOKUP_ESTABLISHED);
+
+ if (priv->sreg_addr)
+ memcpy(&taddr, ®s->data[priv->sreg_addr], sizeof(taddr));
+ taddr = *nf_tproxy_laddr6(skb, &taddr, &iph->daddr);
+
+ if (priv->sreg_port)
+ tport = regs->data[priv->sreg_port];
+ if (!tport)
+ tport = hp->dest;
+
+ /* UDP has no TCP_TIME_WAIT state, so we never enter here */
+ if (sk && sk->sk_state == TCP_TIME_WAIT) {
+ /* reopening a TIME_WAIT connection needs special handling */
+ sk = nf_tproxy_handle_time_wait6(skb, l4proto, thoff,
+ nft_net(pkt),
+ &taddr,
+ tport,
+ sk);
+ } else if (!sk) {
+ /* no there's no established connection, check if
+ * there's a listener on the redirected addr/port
+ */
+ sk = nf_tproxy_get_sock_v6(nft_net(pkt), skb, thoff,
+ l4proto, &iph->saddr, &taddr,
+ hp->source, tport,
+ nft_in(pkt), NF_TPROXY_LOOKUP_LISTENER);
+ }
+
+ /* NOTE: assign_sock consumes our sk reference */
+ if (sk && nf_tproxy_sk_is_transparent(sk))
+ nf_tproxy_assign_sock(skb, sk);
+ else
+ regs->verdict.code = NFT_BREAK;
+}
+#endif
+
+static void nft_tproxy_eval(const struct nft_expr *expr,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ const struct nft_tproxy *priv = nft_expr_priv(expr);
+
+ switch (nft_pf(pkt)) {
+ case NFPROTO_IPV4:
+ switch (priv->family) {
+ case NFPROTO_IPV4:
+ case NFPROTO_UNSPEC:
+ nft_tproxy_eval_v4(expr, regs, pkt);
+ return;
+ }
+ break;
+#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
+ case NFPROTO_IPV6:
+ switch (priv->family) {
+ case NFPROTO_IPV6:
+ case NFPROTO_UNSPEC:
+ nft_tproxy_eval_v6(expr, regs, pkt);
+ return;
+ }
+#endif
+ }
+ regs->verdict.code = NFT_BREAK;
+}
+
+static const struct nla_policy nft_tproxy_policy[NFTA_TPROXY_MAX + 1] = {
+ [NFTA_TPROXY_FAMILY] = { .type = NLA_U32 },
+ [NFTA_TPROXY_REG_ADDR] = { .type = NLA_U32 },
+ [NFTA_TPROXY_REG_PORT] = { .type = NLA_U32 },
+};
+
+static int nft_tproxy_init(const struct nft_ctx *ctx,
+ const struct nft_expr *expr,
+ const struct nlattr * const tb[])
+{
+ struct nft_tproxy *priv = nft_expr_priv(expr);
+ unsigned int alen = 0;
+ int err;
+
+ if (!tb[NFTA_TPROXY_FAMILY] ||
+ (!tb[NFTA_TPROXY_REG_ADDR] && !tb[NFTA_TPROXY_REG_PORT]))
+ return -EINVAL;
+
+ priv->family = ntohl(nla_get_be32(tb[NFTA_TPROXY_FAMILY]));
+
+ switch (ctx->family) {
+ case NFPROTO_IPV4:
+ if (priv->family != NFPROTO_IPV4)
+ return -EINVAL;
+ break;
+#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
+ case NFPROTO_IPV6:
+ if (priv->family != NFPROTO_IPV6)
+ return -EINVAL;
+ break;
+#endif
+ case NFPROTO_INET:
+ break;
+ default:
+ return -EOPNOTSUPP;
+ }
+
+ /* Address is specified but the rule family is not set accordingly */
+ if (priv->family == NFPROTO_UNSPEC && tb[NFTA_TPROXY_REG_ADDR])
+ return -EINVAL;
+
+ switch (priv->family) {
+ case NFPROTO_IPV4:
+ alen = FIELD_SIZEOF(union nf_inet_addr, in);
+ err = nf_defrag_ipv4_enable(ctx->net);
+ if (err)
+ return err;
+ break;
+#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
+ case NFPROTO_IPV6:
+ alen = FIELD_SIZEOF(union nf_inet_addr, in6);
+ err = nf_defrag_ipv6_enable(ctx->net);
+ if (err)
+ return err;
+ break;
+#endif
+ case NFPROTO_UNSPEC:
+ /* No address is specified here */
+ err = nf_defrag_ipv4_enable(ctx->net);
+ if (err)
+ return err;
+ err = nf_defrag_ipv6_enable(ctx->net);
+ if (err)
+ return err;
+ break;
+ default:
+ return -EOPNOTSUPP;
+ }
+
+ if (tb[NFTA_TPROXY_REG_ADDR]) {
+ priv->sreg_addr = nft_parse_register(tb[NFTA_TPROXY_REG_ADDR]);
+ err = nft_validate_register_load(priv->sreg_addr, alen);
+ if (err < 0)
+ return err;
+ }
+
+ if (tb[NFTA_TPROXY_REG_PORT]) {
+ priv->sreg_port = nft_parse_register(tb[NFTA_TPROXY_REG_PORT]);
+ err = nft_validate_register_load(priv->sreg_port, sizeof(u16));
+ if (err < 0)
+ return err;
+ }
+
+ return 0;
+}
+
+static int nft_tproxy_dump(struct sk_buff *skb,
+ const struct nft_expr *expr)
+{
+ const struct nft_tproxy *priv = nft_expr_priv(expr);
+
+ if (nla_put_be32(skb, NFTA_TPROXY_FAMILY, htonl(priv->family)))
+ return -1;
+
+ if (priv->sreg_addr &&
+ nft_dump_register(skb, NFTA_TPROXY_REG_ADDR, priv->sreg_addr))
+ return -1;
+
+ if (priv->sreg_port &&
+ nft_dump_register(skb, NFTA_TPROXY_REG_PORT, priv->sreg_port))
+ return -1;
+
+ return 0;
+}
+
+static struct nft_expr_type nft_tproxy_type;
+static const struct nft_expr_ops nft_tproxy_ops = {
+ .type = &nft_tproxy_type,
+ .size = NFT_EXPR_SIZE(sizeof(struct nft_tproxy)),
+ .eval = nft_tproxy_eval,
+ .init = nft_tproxy_init,
+ .dump = nft_tproxy_dump,
+};
+
+static struct nft_expr_type nft_tproxy_type __read_mostly = {
+ .name = "tproxy",
+ .ops = &nft_tproxy_ops,
+ .policy = nft_tproxy_policy,
+ .maxattr = NFTA_TPROXY_MAX,
+ .owner = THIS_MODULE,
+};
+
+static int __init nft_tproxy_module_init(void)
+{
+ return nft_register_expr(&nft_tproxy_type);
+}
+
+static void __exit nft_tproxy_module_exit(void)
+{
+ nft_unregister_expr(&nft_tproxy_type);
+}
+
+module_init(nft_tproxy_module_init);
+module_exit(nft_tproxy_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Máté Eckl");
+MODULE_DESCRIPTION("nf_tables tproxy support module");
+MODULE_ALIAS_NFT_EXPR("tproxy");
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