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| #include <linux/module.h>
#include <linux/kernel.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/sctp.h>
#include <linux/icmp.h>
#include <linux/slab.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/icmp.h> /* for icmp_send */
#include <net/route.h>
#include <net/ip6_checksum.h>
#include <net/netns/generic.h> /* net_generic() */
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#ifdef CONFIG_IP_VS_IPV6
#include <net/ipv6.h>
#include <linux/netfilter_ipv6.h>
#include <net/ip6_route.h>
#endif
#include <net/ip_vs.h>
#include <linux/dns_resolver.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/version.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/icmp.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/kallsyms.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/arp.h>
#include <net/route.h>
#include <net/neighbour.h>
#include <net/netevent.h>
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 32))
#include <net/net_namespace.h>
#endif
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/inet.h>
#include <linux/skbuff.h>
#include <linux/kthread.h>
int icmp_port = 80;
module_param(icmp_port, int, 0644);
struct addhdr {
u32 saddr, daddr;
u16 sport, dport;
u16 len;
u16 magic;
};
static unsigned int local_out(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
{
struct iphdr *iph = ip_hdr(skb);
struct tcphdr *th;
struct icmphdr *icmp;
struct addhdr *add;
int delta;
iph = ip_hdr(skb);
th = tcp_hdr(skb);
if (iph->protocol != IPPROTO_TCP)
return NF_ACCEPT;
if (ntohs(th->source) != icmp_port && ntohs(th->dest) != icmp_port)
return NF_ACCEPT;
if (skb->len + sizeof(struct icmphdr) + sizeof(struct addhdr) > 1500)
return NF_ACCEPT;
delta = sizeof(struct icmphdr) + sizeof(struct addhdr) + sizeof(struct ethhdr) - skb_headroom(skb);
if (delta > 0 && pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC))
return NF_ACCEPT;
iph = ip_hdr(skb);
th = tcp_hdr(skb);
if (skb->ip_summed != CHECKSUM_COMPLETE) {
th->check = 0;
skb->csum = 0;
th->check = tcp_v4_check(skb->len - ip_hdrlen(skb), iph->saddr, iph->daddr, skb_checksum(skb, ip_hdrlen(skb), skb->len - ip_hdrlen(skb), 0));
skb->ip_summed = CHECKSUM_COMPLETE;
}
skb_push(skb, sizeof(struct icmphdr) + sizeof(struct addhdr));
memcpy(skb->data, skb->data + sizeof(struct icmphdr) + sizeof(struct addhdr), ip_hdrlen(skb));
skb_reset_network_header(skb);
iph = ip_hdr(skb);
iph->protocol = IPPROTO_ICMP;
iph->tot_len = htons(skb->len);
icmp = (struct icmphdr *)(skb->data + ip_hdrlen(skb));
icmp->type = ICMP_ECHO;
icmp->code = 0;
icmp->un.echo.id = 1;
icmp->un.echo.sequence = 1;
add = (struct addhdr *)(skb->data + ip_hdrlen(skb) + sizeof(struct icmphdr));
add->saddr = iph->saddr;
add->daddr = iph->daddr;
add->sport = th->source;
add->dport = th->dest;
add->len = skb->len;
add->magic = skb->len;
skb_set_transport_header(skb, ip_hdrlen(skb));
icmp->checksum = 0;
icmp->checksum = csum_fold(csum_partial(skb->data + ip_hdrlen(skb), skb->len - ip_hdrlen(skb), 0));
ip_send_check(iph);
skb->ip_summed = CHECKSUM_NONE;
return NF_ACCEPT;
}
static unsigned int pre_route(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
{
struct iphdr *iph;
struct tcphdr *th;
struct icmphdr *icmp;
struct addhdr *add;
if (!pskb_may_pull(skb, sizeof(struct iphdr) + sizeof(struct tcphdr) + sizeof(struct icmphdr) + sizeof(struct addhdr)))
return NF_ACCEPT;
iph = ip_hdr(skb);
if (iph->protocol != IPPROTO_ICMP)
return NF_ACCEPT;
icmp = (struct icmphdr*)(skb->data + ip_hdrlen(skb));
if (icmp->type != ICMP_ECHO || icmp->code != 0)
return NF_ACCEPT;
add = (struct addhdr*)(skb->data + ip_hdrlen(skb) + sizeof(struct icmphdr));
th = (struct tcphdr*)(skb->data + ip_hdrlen(skb) + sizeof(struct icmphdr) + sizeof(struct addhdr));
if (ntohs(th->source) != icmp_port && ntohs(th->dest) != icmp_port)
return NF_ACCEPT;
//if (add->saddr != iph->saddr || add->daddr != iph->daddr ||
if (add->sport != th->source || add->dport != th->dest || add->len != skb->len || add->magic != skb->len)
return NF_ACCEPT;
skb_pull(skb, sizeof(struct icmphdr) + sizeof(struct addhdr));
// sizeof(struct icmphdr) + sizeof(struct addhdr) > ip_hdrlen(skb)
memcpy(skb->data, skb->data - sizeof(struct icmphdr) - sizeof(struct addhdr), ip_hdrlen(skb));
memcpy(skb->data - sizeof(struct ethhdr), skb->data - sizeof(struct icmphdr) - sizeof(struct addhdr) - sizeof(struct ethhdr), sizeof(struct ethhdr));
skb_reset_network_header(skb);
iph = ip_hdr(skb);
iph->protocol = IPPROTO_TCP;
iph->tot_len = htons(skb->len);
ip_send_check(iph);
skb->ip_summed = CHECKSUM_UNNECESSARY;
skb_set_transport_header(skb, ip_hdrlen(skb));
th = tcp_hdr(skb);
skb_set_mac_header(skb, -(int)sizeof(struct ethhdr));
return NF_ACCEPT;
}
static const struct nf_hook_ops ip_vs_ops[] = {
{
.hook = local_out,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_LOCAL_OUT,
.priority = 0,
},
{
.hook = pre_route,
.pf = NFPROTO_IPV4,
.hooknum = NF_INET_PRE_ROUTING,
.priority = 0,
},
};
static int net_init(void)
{
if (nf_register_net_hooks(&init_net, ip_vs_ops, ARRAY_SIZE(ip_vs_ops)))
return -1;
return 0;
}
static void net_cleanup(void)
{
nf_unregister_net_hooks(&init_net, ip_vs_ops, ARRAY_SIZE(ip_vs_ops));
}
module_init(net_init);
module_exit(net_cleanup);
MODULE_LICENSE("GPL");
|
