// SPDX-License-Identifier: GPL-2.0#include <linux/types.h>#include <net/ip.h>#include <net/tcp.h>#include <net/netlink.h>#include <net/netfilter/nf_tables.h>#include <net/netfilter/nf_conntrack.h>#include <net/netfilter/nf_conntrack_synproxy.h>#include <net/netfilter/nf_synproxy.h>#include <linux/netfilter_ipv4.h>#include <linux/netfilter/nf_tables.h>#include <linux/netfilter/nf_synproxy.h> struct nft_synproxy {	struct nf_synproxy_info	info;}; static const struct nla_policy nft_synproxy_policy[NFTA_SYNPROXY_MAX + 1] = {	[NFTA_SYNPROXY_MSS]		= { .type = NLA_U16 },	[NFTA_SYNPROXY_WSCALE]		= NLA_POLICY_MAX(NLA_U8, TCP_MAX_WSCALE),	[NFTA_SYNPROXY_FLAGS]		= NLA_POLICY_MASK(NLA_BE32, NF_SYNPROXY_OPT_MASK),}; static void nft_synproxy_tcp_options(struct synproxy_options *opts,				     const struct tcphdr *tcp,				     struct synproxy_net *snet,				     struct nf_synproxy_info *info){	this_cpu_inc(snet->stats->syn_received);	if (tcp->ece && tcp->cwr)		opts->options |= NF_SYNPROXY_OPT_ECN; 	opts->options &= info->options;	opts->mss_encode = opts->mss_option;	opts->mss_option = info->mss;	if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)		synproxy_init_timestamp_cookie(info, opts);	else		opts->options &= ~(NF_SYNPROXY_OPT_WSCALE |				   NF_SYNPROXY_OPT_SACK_PERM |				   NF_SYNPROXY_OPT_ECN);} static void nft_synproxy_eval_v4(const struct nft_synproxy *priv,				 struct nft_regs *regs,				 const struct nft_pktinfo *pkt,				 const struct tcphdr *tcp,				 struct tcphdr *_tcph,				 struct synproxy_options *opts){	struct nf_synproxy_info info = READ_ONCE(priv->info);	struct net *net = nft_net(pkt);	struct synproxy_net *snet = synproxy_pernet(net);	struct sk_buff *skb = pkt->skb; 	if (tcp->syn) {		/* Initial SYN from client */		nft_synproxy_tcp_options(opts, tcp, snet, &info);		synproxy_send_client_synack(net, skb, tcp, opts);		consume_skb(skb);		regs->verdict.code = NF_STOLEN;	} else if (tcp->ack) {		/* ACK from client */		if (synproxy_recv_client_ack(net, skb, tcp, opts,					     ntohl(tcp->seq))) {			consume_skb(skb);			regs->verdict.code = NF_STOLEN;		} else {			regs->verdict.code = NF_DROP;		}	}} #if IS_ENABLED(CONFIG_NF_TABLES_IPV6)static void nft_synproxy_eval_v6(const struct nft_synproxy *priv,				 struct nft_regs *regs,				 const struct nft_pktinfo *pkt,				 const struct tcphdr *tcp,				 struct tcphdr *_tcph,				 struct synproxy_options *opts){	struct nf_synproxy_info info = READ_ONCE(priv->info);	struct net *net = nft_net(pkt);	struct synproxy_net *snet = synproxy_pernet(net);	struct sk_buff *skb = pkt->skb; 	if (tcp->syn) {		/* Initial SYN from client */		nft_synproxy_tcp_options(opts, tcp, snet, &info);		synproxy_send_client_synack_ipv6(net, skb, tcp, opts);		consume_skb(skb);		regs->verdict.code = NF_STOLEN;	} else if (tcp->ack) {		/* ACK from client */		if (synproxy_recv_client_ack_ipv6(net, skb, tcp, opts,						  ntohl(tcp->seq))) {			consume_skb(skb);			regs->verdict.code = NF_STOLEN;		} else {			regs->verdict.code = NF_DROP;		}	}}#endif /* CONFIG_NF_TABLES_IPV6*/ static void nft_synproxy_do_eval(const struct nft_synproxy *priv,				 struct nft_regs *regs,				 const struct nft_pktinfo *pkt){	struct synproxy_options opts = {};	struct sk_buff *skb = pkt->skb;	int thoff = nft_thoff(pkt);	const struct tcphdr *tcp;	struct tcphdr _tcph; 	if (pkt->tprot != IPPROTO_TCP) {		regs->verdict.code = NFT_BREAK;		return;	} 	if (nf_ip_checksum(skb, nft_hook(pkt), thoff, IPPROTO_TCP)) {		regs->verdict.code = NF_DROP;		return;	} 	tcp = skb_header_pointer(skb, thoff,				 sizeof(struct tcphdr),				 &_tcph);	if (!tcp) {		regs->verdict.code = NF_DROP;		return;	} 	if (!synproxy_parse_options(skb, thoff, tcp, &opts)) {		regs->verdict.code = NF_DROP;		return;	} 	switch (skb->protocol) {	case htons(ETH_P_IP):		nft_synproxy_eval_v4(priv, regs, pkt, tcp, &_tcph, &opts);		return;#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)	case htons(ETH_P_IPV6):		nft_synproxy_eval_v6(priv, regs, pkt, tcp, &_tcph, &opts);		return;#endif	}	regs->verdict.code = NFT_BREAK;} static int nft_synproxy_do_init(const struct nft_ctx *ctx,				const struct nlattr * const tb[],				struct nft_synproxy *priv){	struct synproxy_net *snet = synproxy_pernet(ctx->net);	u32 flags;	int err; 	if (tb[NFTA_SYNPROXY_MSS])		priv->info.mss = ntohs(nla_get_be16(tb[NFTA_SYNPROXY_MSS]));	if (tb[NFTA_SYNPROXY_WSCALE])		priv->info.wscale = nla_get_u8(tb[NFTA_SYNPROXY_WSCALE]);	if (tb[NFTA_SYNPROXY_FLAGS]) {		flags = ntohl(nla_get_be32(tb[NFTA_SYNPROXY_FLAGS]));		if (flags & ~NF_SYNPROXY_OPT_MASK)			return -EOPNOTSUPP;		priv->info.options = flags;	} 	err = nf_ct_netns_get(ctx->net, ctx->family);	if (err)		return err; 	switch (ctx->family) {	case NFPROTO_IPV4:		err = nf_synproxy_ipv4_init(snet, ctx->net);		if (err)			goto nf_ct_failure;		break;#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)	case NFPROTO_IPV6:		err = nf_synproxy_ipv6_init(snet, ctx->net);		if (err)			goto nf_ct_failure;		break;#endif	case NFPROTO_INET:		err = nf_synproxy_ipv4_init(snet, ctx->net);		if (err)			goto nf_ct_failure;		err = nf_synproxy_ipv6_init(snet, ctx->net);		if (err) {			nf_synproxy_ipv4_fini(snet, ctx->net);			goto nf_ct_failure;		}		break;	} 	return 0; nf_ct_failure:	nf_ct_netns_put(ctx->net, ctx->family);	return err;} static void nft_synproxy_do_destroy(const struct nft_ctx *ctx){	struct synproxy_net *snet = synproxy_pernet(ctx->net); 	switch (ctx->family) {	case NFPROTO_IPV4:		nf_synproxy_ipv4_fini(snet, ctx->net);		break;#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)	case NFPROTO_IPV6:		nf_synproxy_ipv6_fini(snet, ctx->net);		break;#endif	case NFPROTO_INET:		nf_synproxy_ipv4_fini(snet, ctx->net);		nf_synproxy_ipv6_fini(snet, ctx->net);		break;	}	nf_ct_netns_put(ctx->net, ctx->family);} static int nft_synproxy_do_dump(struct sk_buff *skb, struct nft_synproxy *priv){	if (nla_put_be16(skb, NFTA_SYNPROXY_MSS, htons(priv->info.mss)) ||	    nla_put_u8(skb, NFTA_SYNPROXY_WSCALE, priv->info.wscale) ||	    nla_put_be32(skb, NFTA_SYNPROXY_FLAGS, htonl(priv->info.options)))		goto nla_put_failure; 	return 0; nla_put_failure:	return -1;} static void nft_synproxy_eval(const struct nft_expr *expr,			      struct nft_regs *regs,			      const struct nft_pktinfo *pkt){	const struct nft_synproxy *priv = nft_expr_priv(expr); 	nft_synproxy_do_eval(priv, regs, pkt);} static int nft_synproxy_validate(const struct nft_ctx *ctx,				 const struct nft_expr *expr){	if (ctx->family != NFPROTO_IPV4 &&	    ctx->family != NFPROTO_IPV6 &&	    ctx->family != NFPROTO_INET)		return -EOPNOTSUPP; 	return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) |						    (1 << NF_INET_FORWARD));} static int nft_synproxy_init(const struct nft_ctx *ctx,			     const struct nft_expr *expr,			     const struct nlattr * const tb[]){	struct nft_synproxy *priv = nft_expr_priv(expr); 	return nft_synproxy_do_init(ctx, tb, priv);} static void nft_synproxy_destroy(const struct nft_ctx *ctx,				 const struct nft_expr *expr){	nft_synproxy_do_destroy(ctx);} static int nft_synproxy_dump(struct sk_buff *skb,			     const struct nft_expr *expr, bool reset){	struct nft_synproxy *priv = nft_expr_priv(expr); 	return nft_synproxy_do_dump(skb, priv);} static struct nft_expr_type nft_synproxy_type;static const struct nft_expr_ops nft_synproxy_ops = {	.eval		= nft_synproxy_eval,	.size		= NFT_EXPR_SIZE(sizeof(struct nft_synproxy)),	.init		= nft_synproxy_init,	.destroy	= nft_synproxy_destroy,	.dump		= nft_synproxy_dump,	.type		= &nft_synproxy_type,	.validate	= nft_synproxy_validate,}; static struct nft_expr_type nft_synproxy_type __read_mostly = {	.ops		= &nft_synproxy_ops,	.name		= "synproxy",	.owner		= THIS_MODULE,	.policy		= nft_synproxy_policy,	.maxattr	= NFTA_SYNPROXY_MAX,}; static int nft_synproxy_obj_init(const struct nft_ctx *ctx,				 const struct nlattr * const tb[],				 struct nft_object *obj){	struct nft_synproxy *priv = nft_obj_data(obj); 	return nft_synproxy_do_init(ctx, tb, priv);} static void nft_synproxy_obj_destroy(const struct nft_ctx *ctx,				     struct nft_object *obj){	nft_synproxy_do_destroy(ctx);} static int nft_synproxy_obj_dump(struct sk_buff *skb,				 struct nft_object *obj, bool reset){	struct nft_synproxy *priv = nft_obj_data(obj); 	return nft_synproxy_do_dump(skb, priv);} static void nft_synproxy_obj_eval(struct nft_object *obj,				  struct nft_regs *regs,				  const struct nft_pktinfo *pkt){	const struct nft_synproxy *priv = nft_obj_data(obj); 	nft_synproxy_do_eval(priv, regs, pkt);} static void nft_synproxy_obj_update(struct nft_object *obj,				    struct nft_object *newobj){	struct nft_synproxy *newpriv = nft_obj_data(newobj);	struct nft_synproxy *priv = nft_obj_data(obj); 	WRITE_ONCE(priv->info, newpriv->info);} static struct nft_object_type nft_synproxy_obj_type;static const struct nft_object_ops nft_synproxy_obj_ops = {	.type		= &nft_synproxy_obj_type,	.size		= sizeof(struct nft_synproxy),	.init		= nft_synproxy_obj_init,	.destroy	= nft_synproxy_obj_destroy,	.dump		= nft_synproxy_obj_dump,	.eval		= nft_synproxy_obj_eval,	.update		= nft_synproxy_obj_update,}; static struct nft_object_type nft_synproxy_obj_type __read_mostly = {	.type		= NFT_OBJECT_SYNPROXY,	.ops		= &nft_synproxy_obj_ops,	.maxattr	= NFTA_SYNPROXY_MAX,	.policy		= nft_synproxy_policy,	.owner		= THIS_MODULE,}; static int __init nft_synproxy_module_init(void){	int err; 	err = nft_register_obj(&nft_synproxy_obj_type);	if (err < 0)		return err; 	err = nft_register_expr(&nft_synproxy_type);	if (err < 0)		goto err; 	return 0; err:	nft_unregister_obj(&nft_synproxy_obj_type);	return err;} static void __exit nft_synproxy_module_exit(void){	nft_unregister_expr(&nft_synproxy_type);	nft_unregister_obj(&nft_synproxy_obj_type);} module_init(nft_synproxy_module_init);module_exit(nft_synproxy_module_exit); MODULE_LICENSE("GPL");MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");MODULE_ALIAS_NFT_EXPR("synproxy");MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_SYNPROXY);MODULE_DESCRIPTION("nftables SYNPROXY expression support");