// SPDX-License-Identifier: GPL-2.0
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#include <linux/types.h>
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#include <net/ip.h>
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#include <net/tcp.h>
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#include <net/netlink.h>
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#include <net/netfilter/nf_tables.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_synproxy.h>
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#include <net/netfilter/nf_synproxy.h>
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#include <linux/netfilter/nf_tables.h>
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#include <linux/netfilter/nf_synproxy.h>
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struct nft_synproxy {
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struct nf_synproxy_info info;
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};
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static const struct nla_policy nft_synproxy_policy[NFTA_SYNPROXY_MAX + 1] = {
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[NFTA_SYNPROXY_MSS] = { .type = NLA_U16 },
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[NFTA_SYNPROXY_WSCALE] = { .type = NLA_U8 },
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[NFTA_SYNPROXY_FLAGS] = { .type = NLA_U32 },
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};
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static void nft_synproxy_tcp_options(struct synproxy_options *opts,
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const struct tcphdr *tcp,
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struct synproxy_net *snet,
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struct nf_synproxy_info *info,
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const struct nft_synproxy *priv)
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{
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this_cpu_inc(snet->stats->syn_received);
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if (tcp->ece && tcp->cwr)
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opts->options |= NF_SYNPROXY_OPT_ECN;
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opts->options &= priv->info.options;
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opts->mss_encode = opts->mss_option;
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opts->mss_option = info->mss;
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if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
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synproxy_init_timestamp_cookie(info, opts);
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else
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opts->options &= ~(NF_SYNPROXY_OPT_WSCALE |
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NF_SYNPROXY_OPT_SACK_PERM |
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NF_SYNPROXY_OPT_ECN);
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}
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static void nft_synproxy_eval_v4(const struct nft_synproxy *priv,
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struct nft_regs *regs,
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const struct nft_pktinfo *pkt,
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const struct tcphdr *tcp,
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struct tcphdr *_tcph,
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struct synproxy_options *opts)
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{
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struct nf_synproxy_info info = priv->info;
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struct net *net = nft_net(pkt);
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struct synproxy_net *snet = synproxy_pernet(net);
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struct sk_buff *skb = pkt->skb;
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if (tcp->syn) {
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/* Initial SYN from client */
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nft_synproxy_tcp_options(opts, tcp, snet, &info, priv);
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synproxy_send_client_synack(net, skb, tcp, opts);
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consume_skb(skb);
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regs->verdict.code = NF_STOLEN;
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} else if (tcp->ack) {
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/* ACK from client */
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if (synproxy_recv_client_ack(net, skb, tcp, opts,
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ntohl(tcp->seq))) {
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consume_skb(skb);
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regs->verdict.code = NF_STOLEN;
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} else {
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regs->verdict.code = NF_DROP;
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}
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}
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}
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#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
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static void nft_synproxy_eval_v6(const struct nft_synproxy *priv,
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struct nft_regs *regs,
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const struct nft_pktinfo *pkt,
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const struct tcphdr *tcp,
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struct tcphdr *_tcph,
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struct synproxy_options *opts)
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{
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struct nf_synproxy_info info = priv->info;
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struct net *net = nft_net(pkt);
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struct synproxy_net *snet = synproxy_pernet(net);
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struct sk_buff *skb = pkt->skb;
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if (tcp->syn) {
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/* Initial SYN from client */
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nft_synproxy_tcp_options(opts, tcp, snet, &info, priv);
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synproxy_send_client_synack_ipv6(net, skb, tcp, opts);
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consume_skb(skb);
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regs->verdict.code = NF_STOLEN;
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} else if (tcp->ack) {
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/* ACK from client */
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if (synproxy_recv_client_ack_ipv6(net, skb, tcp, opts,
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ntohl(tcp->seq))) {
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consume_skb(skb);
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regs->verdict.code = NF_STOLEN;
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} else {
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regs->verdict.code = NF_DROP;
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}
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}
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}
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#endif /* CONFIG_NF_TABLES_IPV6*/
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static void nft_synproxy_do_eval(const struct nft_synproxy *priv,
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struct nft_regs *regs,
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const struct nft_pktinfo *pkt)
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{
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struct synproxy_options opts = {};
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struct sk_buff *skb = pkt->skb;
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int thoff = pkt->xt.thoff;
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const struct tcphdr *tcp;
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struct tcphdr _tcph;
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if (pkt->tprot != IPPROTO_TCP) {
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regs->verdict.code = NFT_BREAK;
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return;
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}
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if (nf_ip_checksum(skb, nft_hook(pkt), thoff, IPPROTO_TCP)) {
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regs->verdict.code = NF_DROP;
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return;
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}
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tcp = skb_header_pointer(skb, pkt->xt.thoff,
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sizeof(struct tcphdr),
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&_tcph);
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if (!tcp) {
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regs->verdict.code = NF_DROP;
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return;
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}
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if (!synproxy_parse_options(skb, thoff, tcp, &opts)) {
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regs->verdict.code = NF_DROP;
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return;
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}
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switch (skb->protocol) {
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case htons(ETH_P_IP):
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nft_synproxy_eval_v4(priv, regs, pkt, tcp, &_tcph, &opts);
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return;
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#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
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case htons(ETH_P_IPV6):
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nft_synproxy_eval_v6(priv, regs, pkt, tcp, &_tcph, &opts);
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return;
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#endif
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}
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regs->verdict.code = NFT_BREAK;
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}
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static int nft_synproxy_do_init(const struct nft_ctx *ctx,
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const struct nlattr * const tb[],
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struct nft_synproxy *priv)
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{
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struct synproxy_net *snet = synproxy_pernet(ctx->net);
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u32 flags;
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int err;
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if (tb[NFTA_SYNPROXY_MSS])
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priv->info.mss = ntohs(nla_get_be16(tb[NFTA_SYNPROXY_MSS]));
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if (tb[NFTA_SYNPROXY_WSCALE])
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priv->info.wscale = nla_get_u8(tb[NFTA_SYNPROXY_WSCALE]);
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if (tb[NFTA_SYNPROXY_FLAGS]) {
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flags = ntohl(nla_get_be32(tb[NFTA_SYNPROXY_FLAGS]));
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if (flags & ~NF_SYNPROXY_OPT_MASK)
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return -EOPNOTSUPP;
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priv->info.options = flags;
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}
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err = nf_ct_netns_get(ctx->net, ctx->family);
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if (err)
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return err;
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switch (ctx->family) {
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case NFPROTO_IPV4:
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err = nf_synproxy_ipv4_init(snet, ctx->net);
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if (err)
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goto nf_ct_failure;
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break;
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#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
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case NFPROTO_IPV6:
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err = nf_synproxy_ipv6_init(snet, ctx->net);
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if (err)
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goto nf_ct_failure;
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break;
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#endif
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case NFPROTO_INET:
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case NFPROTO_BRIDGE:
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err = nf_synproxy_ipv4_init(snet, ctx->net);
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if (err)
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goto nf_ct_failure;
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err = nf_synproxy_ipv6_init(snet, ctx->net);
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if (err) {
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nf_synproxy_ipv4_fini(snet, ctx->net);
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goto nf_ct_failure;
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}
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break;
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}
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return 0;
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nf_ct_failure:
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nf_ct_netns_put(ctx->net, ctx->family);
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return err;
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}
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static void nft_synproxy_do_destroy(const struct nft_ctx *ctx)
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{
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struct synproxy_net *snet = synproxy_pernet(ctx->net);
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switch (ctx->family) {
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case NFPROTO_IPV4:
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nf_synproxy_ipv4_fini(snet, ctx->net);
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break;
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#if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
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case NFPROTO_IPV6:
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nf_synproxy_ipv6_fini(snet, ctx->net);
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break;
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#endif
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case NFPROTO_INET:
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case NFPROTO_BRIDGE:
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nf_synproxy_ipv4_fini(snet, ctx->net);
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nf_synproxy_ipv6_fini(snet, ctx->net);
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break;
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}
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nf_ct_netns_put(ctx->net, ctx->family);
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}
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static int nft_synproxy_do_dump(struct sk_buff *skb, struct nft_synproxy *priv)
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{
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if (nla_put_be16(skb, NFTA_SYNPROXY_MSS, htons(priv->info.mss)) ||
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nla_put_u8(skb, NFTA_SYNPROXY_WSCALE, priv->info.wscale) ||
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nla_put_be32(skb, NFTA_SYNPROXY_FLAGS, htonl(priv->info.options)))
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goto nla_put_failure;
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return 0;
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nla_put_failure:
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return -1;
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}
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static void nft_synproxy_eval(const struct nft_expr *expr,
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struct nft_regs *regs,
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const struct nft_pktinfo *pkt)
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{
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const struct nft_synproxy *priv = nft_expr_priv(expr);
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nft_synproxy_do_eval(priv, regs, pkt);
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}
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static int nft_synproxy_validate(const struct nft_ctx *ctx,
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const struct nft_expr *expr,
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const struct nft_data **data)
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{
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return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) |
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(1 << NF_INET_FORWARD));
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}
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static int nft_synproxy_init(const struct nft_ctx *ctx,
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const struct nft_expr *expr,
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const struct nlattr * const tb[])
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{
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struct nft_synproxy *priv = nft_expr_priv(expr);
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return nft_synproxy_do_init(ctx, tb, priv);
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}
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static void nft_synproxy_destroy(const struct nft_ctx *ctx,
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const struct nft_expr *expr)
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{
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nft_synproxy_do_destroy(ctx);
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}
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static int nft_synproxy_dump(struct sk_buff *skb, const struct nft_expr *expr)
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{
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struct nft_synproxy *priv = nft_expr_priv(expr);
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return nft_synproxy_do_dump(skb, priv);
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}
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static struct nft_expr_type nft_synproxy_type;
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static const struct nft_expr_ops nft_synproxy_ops = {
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.eval = nft_synproxy_eval,
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.size = NFT_EXPR_SIZE(sizeof(struct nft_synproxy)),
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.init = nft_synproxy_init,
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.destroy = nft_synproxy_destroy,
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.dump = nft_synproxy_dump,
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.type = &nft_synproxy_type,
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.validate = nft_synproxy_validate,
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};
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static struct nft_expr_type nft_synproxy_type __read_mostly = {
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.ops = &nft_synproxy_ops,
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.name = "synproxy",
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.owner = THIS_MODULE,
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.policy = nft_synproxy_policy,
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.maxattr = NFTA_SYNPROXY_MAX,
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};
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static int nft_synproxy_obj_init(const struct nft_ctx *ctx,
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const struct nlattr * const tb[],
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struct nft_object *obj)
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{
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struct nft_synproxy *priv = nft_obj_data(obj);
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return nft_synproxy_do_init(ctx, tb, priv);
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}
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static void nft_synproxy_obj_destroy(const struct nft_ctx *ctx,
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struct nft_object *obj)
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{
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nft_synproxy_do_destroy(ctx);
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}
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static int nft_synproxy_obj_dump(struct sk_buff *skb,
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struct nft_object *obj, bool reset)
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{
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struct nft_synproxy *priv = nft_obj_data(obj);
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return nft_synproxy_do_dump(skb, priv);
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}
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static void nft_synproxy_obj_eval(struct nft_object *obj,
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struct nft_regs *regs,
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const struct nft_pktinfo *pkt)
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{
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const struct nft_synproxy *priv = nft_obj_data(obj);
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nft_synproxy_do_eval(priv, regs, pkt);
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}
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static void nft_synproxy_obj_update(struct nft_object *obj,
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struct nft_object *newobj)
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{
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struct nft_synproxy *newpriv = nft_obj_data(newobj);
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struct nft_synproxy *priv = nft_obj_data(obj);
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priv->info = newpriv->info;
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}
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static struct nft_object_type nft_synproxy_obj_type;
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static const struct nft_object_ops nft_synproxy_obj_ops = {
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.type = &nft_synproxy_obj_type,
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.size = sizeof(struct nft_synproxy),
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.init = nft_synproxy_obj_init,
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.destroy = nft_synproxy_obj_destroy,
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.dump = nft_synproxy_obj_dump,
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.eval = nft_synproxy_obj_eval,
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.update = nft_synproxy_obj_update,
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};
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static struct nft_object_type nft_synproxy_obj_type __read_mostly = {
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.type = NFT_OBJECT_SYNPROXY,
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.ops = &nft_synproxy_obj_ops,
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.maxattr = NFTA_SYNPROXY_MAX,
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.policy = nft_synproxy_policy,
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.owner = THIS_MODULE,
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};
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static int __init nft_synproxy_module_init(void)
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{
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int err;
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err = nft_register_obj(&nft_synproxy_obj_type);
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if (err < 0)
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return err;
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err = nft_register_expr(&nft_synproxy_type);
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if (err < 0)
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goto err;
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return 0;
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err:
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nft_unregister_obj(&nft_synproxy_obj_type);
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return err;
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}
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static void __exit nft_synproxy_module_exit(void)
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{
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nft_unregister_expr(&nft_synproxy_type);
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nft_unregister_obj(&nft_synproxy_obj_type);
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}
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module_init(nft_synproxy_module_init);
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module_exit(nft_synproxy_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
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MODULE_ALIAS_NFT_EXPR("synproxy");
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MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_SYNPROXY);
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MODULE_DESCRIPTION("nftables SYNPROXY expression support");
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