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