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Diffstat (limited to 'net/ipv4/netfilter/ipt_REJECT.c')
-rw-r--r--net/ipv4/netfilter/ipt_REJECT.c335
1 files changed, 335 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/ipt_REJECT.c b/net/ipv4/netfilter/ipt_REJECT.c
new file mode 100644
index 00000000000..266d6497928
--- /dev/null
+++ b/net/ipv4/netfilter/ipt_REJECT.c
@@ -0,0 +1,335 @@
+/*
+ * This is a module which is used for rejecting packets.
+ * Added support for customized reject packets (Jozsef Kadlecsik).
+ * Added support for ICMP type-3-code-13 (Maciej Soltysiak). [RFC 1812]
+ */
+
+/* (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/config.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+#include <linux/icmp.h>
+#include <net/icmp.h>
+#include <net/ip.h>
+#include <net/tcp.h>
+#include <net/route.h>
+#include <net/dst.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_REJECT.h>
+#ifdef CONFIG_BRIDGE_NETFILTER
+#include <linux/netfilter_bridge.h>
+#endif
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
+MODULE_DESCRIPTION("iptables REJECT target module");
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+static inline struct rtable *route_reverse(struct sk_buff *skb,
+ struct tcphdr *tcph, int hook)
+{
+ struct iphdr *iph = skb->nh.iph;
+ struct dst_entry *odst;
+ struct flowi fl = {};
+ struct rtable *rt;
+
+ /* We don't require ip forwarding to be enabled to be able to
+ * send a RST reply for bridged traffic. */
+ if (hook != NF_IP_FORWARD
+#ifdef CONFIG_BRIDGE_NETFILTER
+ || (skb->nf_bridge && skb->nf_bridge->mask & BRNF_BRIDGED)
+#endif
+ ) {
+ fl.nl_u.ip4_u.daddr = iph->saddr;
+ if (hook == NF_IP_LOCAL_IN)
+ fl.nl_u.ip4_u.saddr = iph->daddr;
+ fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
+
+ if (ip_route_output_key(&rt, &fl) != 0)
+ return NULL;
+ } else {
+ /* non-local src, find valid iif to satisfy
+ * rp-filter when calling ip_route_input. */
+ fl.nl_u.ip4_u.daddr = iph->daddr;
+ if (ip_route_output_key(&rt, &fl) != 0)
+ return NULL;
+
+ odst = skb->dst;
+ if (ip_route_input(skb, iph->saddr, iph->daddr,
+ RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
+ dst_release(&rt->u.dst);
+ return NULL;
+ }
+ dst_release(&rt->u.dst);
+ rt = (struct rtable *)skb->dst;
+ skb->dst = odst;
+
+ fl.nl_u.ip4_u.daddr = iph->saddr;
+ fl.nl_u.ip4_u.saddr = iph->daddr;
+ fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
+ }
+
+ if (rt->u.dst.error) {
+ dst_release(&rt->u.dst);
+ return NULL;
+ }
+
+ fl.proto = IPPROTO_TCP;
+ fl.fl_ip_sport = tcph->dest;
+ fl.fl_ip_dport = tcph->source;
+
+ if (xfrm_lookup((struct dst_entry **)&rt, &fl, NULL, 0)) {
+ dst_release(&rt->u.dst);
+ rt = NULL;
+ }
+
+ return rt;
+}
+
+/* Send RST reply */
+static void send_reset(struct sk_buff *oldskb, int hook)
+{
+ struct sk_buff *nskb;
+ struct tcphdr _otcph, *oth, *tcph;
+ struct rtable *rt;
+ u_int16_t tmp_port;
+ u_int32_t tmp_addr;
+ int needs_ack;
+ int hh_len;
+
+ /* IP header checks: fragment. */
+ if (oldskb->nh.iph->frag_off & htons(IP_OFFSET))
+ return;
+
+ oth = skb_header_pointer(oldskb, oldskb->nh.iph->ihl * 4,
+ sizeof(_otcph), &_otcph);
+ if (oth == NULL)
+ return;
+
+ /* No RST for RST. */
+ if (oth->rst)
+ return;
+
+ /* FIXME: Check checksum --RR */
+ if ((rt = route_reverse(oldskb, oth, hook)) == NULL)
+ return;
+
+ hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
+
+ /* We need a linear, writeable skb. We also need to expand
+ headroom in case hh_len of incoming interface < hh_len of
+ outgoing interface */
+ nskb = skb_copy_expand(oldskb, hh_len, skb_tailroom(oldskb),
+ GFP_ATOMIC);
+ if (!nskb) {
+ dst_release(&rt->u.dst);
+ return;
+ }
+
+ dst_release(nskb->dst);
+ nskb->dst = &rt->u.dst;
+
+ /* This packet will not be the same as the other: clear nf fields */
+ nf_reset(nskb);
+ nskb->nfcache = 0;
+ nskb->nfmark = 0;
+#ifdef CONFIG_BRIDGE_NETFILTER
+ nf_bridge_put(nskb->nf_bridge);
+ nskb->nf_bridge = NULL;
+#endif
+
+ tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);
+
+ /* Swap source and dest */
+ tmp_addr = nskb->nh.iph->saddr;
+ nskb->nh.iph->saddr = nskb->nh.iph->daddr;
+ nskb->nh.iph->daddr = tmp_addr;
+ tmp_port = tcph->source;
+ tcph->source = tcph->dest;
+ tcph->dest = tmp_port;
+
+ /* Truncate to length (no data) */
+ tcph->doff = sizeof(struct tcphdr)/4;
+ skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr));
+ nskb->nh.iph->tot_len = htons(nskb->len);
+
+ if (tcph->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
+ + oldskb->len - oldskb->nh.iph->ihl*4
+ - (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;
+
+ /* Adjust TCP checksum */
+ tcph->check = 0;
+ tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr),
+ nskb->nh.iph->saddr,
+ nskb->nh.iph->daddr,
+ csum_partial((char *)tcph,
+ sizeof(struct tcphdr), 0));
+
+ /* Adjust IP TTL, DF */
+ nskb->nh.iph->ttl = MAXTTL;
+ /* Set DF, id = 0 */
+ nskb->nh.iph->frag_off = htons(IP_DF);
+ nskb->nh.iph->id = 0;
+
+ /* Adjust IP checksum */
+ nskb->nh.iph->check = 0;
+ nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph,
+ nskb->nh.iph->ihl);
+
+ /* "Never happens" */
+ if (nskb->len > dst_mtu(nskb->dst))
+ goto free_nskb;
+
+ nf_ct_attach(nskb, oldskb);
+
+ NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
+ dst_output);
+ return;
+
+ free_nskb:
+ kfree_skb(nskb);
+}
+
+static inline void send_unreach(struct sk_buff *skb_in, int code)
+{
+ icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
+}
+
+static unsigned int reject(struct sk_buff **pskb,
+ const struct net_device *in,
+ const struct net_device *out,
+ unsigned int hooknum,
+ const void *targinfo,
+ void *userinfo)
+{
+ const struct ipt_reject_info *reject = targinfo;
+
+ /* Our naive response construction doesn't deal with IP
+ options, and probably shouldn't try. */
+ if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr))
+ return NF_DROP;
+
+ /* WARNING: This code causes reentry within iptables.
+ This means that the iptables jump stack is now crap. We
+ must return an absolute verdict. --RR */
+ switch (reject->with) {
+ case IPT_ICMP_NET_UNREACHABLE:
+ send_unreach(*pskb, ICMP_NET_UNREACH);
+ break;
+ case IPT_ICMP_HOST_UNREACHABLE:
+ send_unreach(*pskb, ICMP_HOST_UNREACH);
+ break;
+ case IPT_ICMP_PROT_UNREACHABLE:
+ send_unreach(*pskb, ICMP_PROT_UNREACH);
+ break;
+ case IPT_ICMP_PORT_UNREACHABLE:
+ send_unreach(*pskb, ICMP_PORT_UNREACH);
+ break;
+ case IPT_ICMP_NET_PROHIBITED:
+ send_unreach(*pskb, ICMP_NET_ANO);
+ break;
+ case IPT_ICMP_HOST_PROHIBITED:
+ send_unreach(*pskb, ICMP_HOST_ANO);
+ break;
+ case IPT_ICMP_ADMIN_PROHIBITED:
+ send_unreach(*pskb, ICMP_PKT_FILTERED);
+ break;
+ case IPT_TCP_RESET:
+ send_reset(*pskb, hooknum);
+ case IPT_ICMP_ECHOREPLY:
+ /* Doesn't happen. */
+ break;
+ }
+
+ return NF_DROP;
+}
+
+static int check(const char *tablename,
+ const struct ipt_entry *e,
+ void *targinfo,
+ unsigned int targinfosize,
+ unsigned int hook_mask)
+{
+ const struct ipt_reject_info *rejinfo = targinfo;
+
+ if (targinfosize != IPT_ALIGN(sizeof(struct ipt_reject_info))) {
+ DEBUGP("REJECT: targinfosize %u != 0\n", targinfosize);
+ return 0;
+ }
+
+ /* Only allow these for packet filtering. */
+ if (strcmp(tablename, "filter") != 0) {
+ DEBUGP("REJECT: bad table `%s'.\n", tablename);
+ return 0;
+ }
+ if ((hook_mask & ~((1 << NF_IP_LOCAL_IN)
+ | (1 << NF_IP_FORWARD)
+ | (1 << NF_IP_LOCAL_OUT))) != 0) {
+ DEBUGP("REJECT: bad hook mask %X\n", hook_mask);
+ return 0;
+ }
+
+ if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
+ printk("REJECT: ECHOREPLY no longer supported.\n");
+ return 0;
+ } else if (rejinfo->with == IPT_TCP_RESET) {
+ /* Must specify that it's a TCP packet */
+ if (e->ip.proto != IPPROTO_TCP
+ || (e->ip.invflags & IPT_INV_PROTO)) {
+ DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
+ return 0;
+ }
+ }
+
+ return 1;
+}
+
+static struct ipt_target ipt_reject_reg = {
+ .name = "REJECT",
+ .target = reject,
+ .checkentry = check,
+ .me = THIS_MODULE,
+};
+
+static int __init init(void)
+{
+ return ipt_register_target(&ipt_reject_reg);
+}
+
+static void __exit fini(void)
+{
+ ipt_unregister_target(&ipt_reject_reg);
+}
+
+module_init(init);
+module_exit(fini);
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