// SPDX-License-Identifier: GPL-2.0-only
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/* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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*/
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#include <linux/module.h>
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#include <net/ipv6.h>
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#include <net/ip6_route.h>
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#include <net/ip6_fib.h>
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#include <net/ip6_checksum.h>
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#include <net/netfilter/ipv6/nf_reject.h>
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#include <linux/netfilter_ipv6.h>
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#include <linux/netfilter_bridge.h>
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const struct tcphdr *nf_reject_ip6_tcphdr_get(struct sk_buff *oldskb,
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struct tcphdr *otcph,
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unsigned int *otcplen, int hook)
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{
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const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
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u8 proto;
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__be16 frag_off;
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int tcphoff;
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proto = oip6h->nexthdr;
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tcphoff = ipv6_skip_exthdr(oldskb, ((u8 *)(oip6h + 1) - oldskb->data),
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&proto, &frag_off);
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if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
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pr_debug("Cannot get TCP header.\n");
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return NULL;
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}
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*otcplen = oldskb->len - tcphoff;
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/* IP header checks: fragment, too short. */
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if (proto != IPPROTO_TCP || *otcplen < sizeof(struct tcphdr)) {
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pr_debug("proto(%d) != IPPROTO_TCP or too short (len = %d)\n",
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proto, *otcplen);
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return NULL;
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}
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otcph = skb_header_pointer(oldskb, tcphoff, sizeof(struct tcphdr),
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otcph);
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if (otcph == NULL)
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return NULL;
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/* No RST for RST. */
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if (otcph->rst) {
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pr_debug("RST is set\n");
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return NULL;
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}
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/* Check checksum. */
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if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) {
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pr_debug("TCP checksum is invalid\n");
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return NULL;
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}
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return otcph;
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}
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EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_get);
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struct ipv6hdr *nf_reject_ip6hdr_put(struct sk_buff *nskb,
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const struct sk_buff *oldskb,
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__u8 protocol, int hoplimit)
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{
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struct ipv6hdr *ip6h;
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const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
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#define DEFAULT_TOS_VALUE 0x0U
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const __u8 tclass = DEFAULT_TOS_VALUE;
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skb_put(nskb, sizeof(struct ipv6hdr));
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skb_reset_network_header(nskb);
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ip6h = ipv6_hdr(nskb);
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ip6_flow_hdr(ip6h, tclass, 0);
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ip6h->hop_limit = hoplimit;
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ip6h->nexthdr = protocol;
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ip6h->saddr = oip6h->daddr;
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ip6h->daddr = oip6h->saddr;
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nskb->protocol = htons(ETH_P_IPV6);
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return ip6h;
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}
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EXPORT_SYMBOL_GPL(nf_reject_ip6hdr_put);
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void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb,
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const struct sk_buff *oldskb,
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const struct tcphdr *oth, unsigned int otcplen)
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{
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struct tcphdr *tcph;
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int needs_ack;
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skb_reset_transport_header(nskb);
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tcph = skb_put(nskb, sizeof(struct tcphdr));
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/* Truncate to length (no data) */
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tcph->doff = sizeof(struct tcphdr)/4;
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tcph->source = oth->dest;
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tcph->dest = oth->source;
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if (oth->ack) {
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needs_ack = 0;
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tcph->seq = oth->ack_seq;
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tcph->ack_seq = 0;
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} else {
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needs_ack = 1;
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tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
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otcplen - (oth->doff<<2));
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tcph->seq = 0;
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}
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/* Reset flags */
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((u_int8_t *)tcph)[13] = 0;
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tcph->rst = 1;
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tcph->ack = needs_ack;
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tcph->window = 0;
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tcph->urg_ptr = 0;
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tcph->check = 0;
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/* Adjust TCP checksum */
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tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
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&ipv6_hdr(nskb)->daddr,
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sizeof(struct tcphdr), IPPROTO_TCP,
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csum_partial(tcph,
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sizeof(struct tcphdr), 0));
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}
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EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_put);
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static int nf_reject6_fill_skb_dst(struct sk_buff *skb_in)
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{
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struct dst_entry *dst = NULL;
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struct flowi fl;
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memset(&fl, 0, sizeof(struct flowi));
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fl.u.ip6.daddr = ipv6_hdr(skb_in)->saddr;
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nf_ip6_route(dev_net(skb_in->dev), &dst, &fl, false);
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if (!dst)
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return -1;
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skb_dst_set(skb_in, dst);
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return 0;
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}
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void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
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{
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struct net_device *br_indev __maybe_unused;
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struct sk_buff *nskb;
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struct tcphdr _otcph;
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const struct tcphdr *otcph;
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unsigned int otcplen, hh_len;
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const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
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struct ipv6hdr *ip6h;
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struct dst_entry *dst = NULL;
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struct flowi6 fl6;
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if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
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(!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
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pr_debug("addr is not unicast.\n");
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return;
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}
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otcph = nf_reject_ip6_tcphdr_get(oldskb, &_otcph, &otcplen, hook);
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if (!otcph)
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return;
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memset(&fl6, 0, sizeof(fl6));
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fl6.flowi6_proto = IPPROTO_TCP;
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fl6.saddr = oip6h->daddr;
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fl6.daddr = oip6h->saddr;
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fl6.fl6_sport = otcph->dest;
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fl6.fl6_dport = otcph->source;
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if (hook == NF_INET_PRE_ROUTING) {
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nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
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if (!dst)
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return;
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skb_dst_set(oldskb, dst);
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}
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fl6.flowi6_oif = l3mdev_master_ifindex(skb_dst(oldskb)->dev);
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fl6.flowi6_mark = IP6_REPLY_MARK(net, oldskb->mark);
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security_skb_classify_flow(oldskb, flowi6_to_flowi_common(&fl6));
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dst = ip6_route_output(net, NULL, &fl6);
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if (dst->error) {
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dst_release(dst);
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return;
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}
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dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
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if (IS_ERR(dst))
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return;
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hh_len = (dst->dev->hard_header_len + 15)&~15;
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nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
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+ sizeof(struct tcphdr) + dst->trailer_len,
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GFP_ATOMIC);
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if (!nskb) {
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net_dbg_ratelimited("cannot alloc skb\n");
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dst_release(dst);
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return;
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}
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skb_dst_set(nskb, dst);
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nskb->mark = fl6.flowi6_mark;
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skb_reserve(nskb, hh_len + dst->header_len);
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ip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
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ip6_dst_hoplimit(dst));
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nf_reject_ip6_tcphdr_put(nskb, oldskb, otcph, otcplen);
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nf_ct_attach(nskb, oldskb);
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#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
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/* If we use ip6_local_out for bridged traffic, the MAC source on
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* the RST will be ours, instead of the destination's. This confuses
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* some routers/firewalls, and they drop the packet. So we need to
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* build the eth header using the original destination's MAC as the
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* source, and send the RST packet directly.
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*/
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br_indev = nf_bridge_get_physindev(oldskb);
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if (br_indev) {
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struct ethhdr *oeth = eth_hdr(oldskb);
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nskb->dev = br_indev;
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nskb->protocol = htons(ETH_P_IPV6);
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ip6h->payload_len = htons(sizeof(struct tcphdr));
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if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
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oeth->h_source, oeth->h_dest, nskb->len) < 0) {
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kfree_skb(nskb);
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return;
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}
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dev_queue_xmit(nskb);
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} else
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#endif
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ip6_local_out(net, nskb->sk, nskb);
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}
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EXPORT_SYMBOL_GPL(nf_send_reset6);
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static bool reject6_csum_ok(struct sk_buff *skb, int hook)
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{
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const struct ipv6hdr *ip6h = ipv6_hdr(skb);
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int thoff;
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__be16 fo;
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u8 proto;
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if (skb_csum_unnecessary(skb))
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return true;
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proto = ip6h->nexthdr;
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thoff = ipv6_skip_exthdr(skb, ((u8 *)(ip6h + 1) - skb->data), &proto, &fo);
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if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
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return false;
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if (!nf_reject_verify_csum(proto))
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return true;
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return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
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}
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void nf_send_unreach6(struct net *net, struct sk_buff *skb_in,
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unsigned char code, unsigned int hooknum)
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{
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if (!reject6_csum_ok(skb_in, hooknum))
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return;
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if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
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skb_in->dev = net->loopback_dev;
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if (hooknum == NF_INET_PRE_ROUTING && nf_reject6_fill_skb_dst(skb_in))
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return;
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icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);
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}
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EXPORT_SYMBOL_GPL(nf_send_unreach6);
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MODULE_LICENSE("GPL");
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