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Code Issues Releases Wiki Activity

xt_ECHO: IPv6 support

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This commit is contained in:
Jan Engelhardt
2011-09-25 14:57:48 +02:00
parent 434dea2b53
commit 487da26146
2 changed files with 128 additions and 11 deletions
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2
doc/changelog.txt
View File

@@ -5,6 +5,8 @@ Fixes:
- xt_ECHO: fix kernel warning about RTAX_HOPLIMIT being used
Changes:
- xt_ECHO: now calculates UDP checksum
Enhancements:
- xt_ECHO: IPv6 support
v1.39 (2011-09-21)

137
extensions/xt_ECHO.c
View File

@@ -1,7 +1,7 @@
/*
* "ECHO" (RFC 862) target extension for Xtables
* Sample module for "Writing your own Netfilter Modules"
* Copyright © Jan Engelhardt <jengelh [at] medozas de>, 2008
* Copyright © Jan Engelhardt <jengelh [at] medozas de>, 2008-2011
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License; either
@@ -18,9 +18,112 @@
# include <linux/netfilter_bridge.h>
#endif
#include <net/ip.h>
#include <net/ip6_route.h>
#include <net/route.h>
#include "compat_xtables.h"
static unsigned int
echo_tg6(struct sk_buff **poldskb, const struct xt_action_param *par)
{
const struct sk_buff *oldskb = *poldskb;
const struct udphdr *oldudp;
const struct ipv6hdr *oldip;
struct udphdr *newudp, oldudp_buf;
struct ipv6hdr *newip;
struct sk_buff *newskb;
unsigned int data_len;
void *payload;
struct flowi6 fl;
struct dst_entry *dst = NULL;
struct net *net = dev_net((par->in != NULL) ? par->in : par->out);
/* This allows us to do the copy operation in fewer lines of code. */
if (skb_linearize(*poldskb) < 0)
return NF_DROP;
oldip = ipv6_hdr(oldskb);
oldudp = skb_header_pointer(oldskb, par->thoff,
sizeof(*oldudp), &oldudp_buf);
if (oldudp == NULL)
return NF_DROP;
if (ntohs(oldudp->len) <= sizeof(*oldudp))
return NF_DROP;
newskb = alloc_skb(LL_MAX_HEADER + sizeof(*newip) +
ntohs(oldudp->len), GFP_ATOMIC);
if (newskb == NULL)
return NF_DROP;
skb_reserve(newskb, LL_MAX_HEADER);
newskb->protocol = oldskb->protocol;
skb_reset_network_header(newskb);
newip = (void *)skb_put(newskb, sizeof(*newip));
newip->version = oldip->version;
newip->priority = oldip->priority;
memcpy(newip->flow_lbl, oldip->flow_lbl, sizeof(newip->flow_lbl));
newip->nexthdr = par->target->proto;
newip->saddr = oldip->daddr;
newip->daddr = oldip->saddr;
skb_reset_transport_header(newskb);
newudp = (void *)skb_put(newskb, sizeof(*newudp));
newudp->source = oldudp->dest;
newudp->dest = oldudp->source;
newudp->len = oldudp->len;
data_len = htons(oldudp->len) - sizeof(*oldudp);
payload = skb_header_pointer(oldskb, par->thoff +
sizeof(*oldudp), data_len, NULL);
memcpy(skb_put(newskb, data_len), payload, data_len);
#if 0
/*
* Since no fields are modified (we just swapped things around),
* this works too in our specific echo case.
*/
newudp->check = oldudp->check;
#else
newudp->check = 0;
newudp->check = csum_ipv6_magic(&newip->saddr, &newip->daddr,
ntohs(newudp->len), IPPROTO_UDP,
csum_partial(newudp, ntohs(newudp->len), 0));
#endif
memset(&fl, 0, sizeof(fl));
fl.flowi6_proto = newip->nexthdr;
ipv6_addr_copy(&fl.saddr, &newip->saddr);
ipv6_addr_copy(&fl.daddr, &newip->daddr);
fl.fl6_sport = newudp->source;
fl.fl6_dport = newudp->dest;
security_skb_classify_flow((struct sk_buff *)oldskb, flowi6_to_flowi(&fl));
dst = ip6_route_output(net, NULL, &fl);
if (dst == NULL || dst->error != 0) {
dst_release(dst);
goto free_nskb;
}
skb_dst_set(newskb, dst);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 38)
newip->hop_limit = ip6_dst_hoplimit(skb_dst(newskb));
#else
newip->hop_limit = dst_metric(skb_dst(newskb), RTAX_HOPLIMIT);
#endif
newskb->ip_summed = CHECKSUM_NONE;
/* "Never happens" (?) */
if (newskb->len > dst_mtu(skb_dst(newskb)))
goto free_nskb;
nf_ct_attach(newskb, *poldskb);
ip6_local_out(newskb);
return NF_DROP;
free_nskb:
kfree_skb(newskb);
return NF_DROP;
}
static unsigned int
echo_tg4(struct sk_buff **poldskb, const struct xt_action_param *par)
{
@@ -115,24 +218,35 @@ echo_tg4(struct sk_buff **poldskb, const struct xt_action_param *par)
return NF_DROP;
}
static struct xt_target echo_tg_reg __read_mostly = {
.name = "ECHO",
.revision = 0,
.family = NFPROTO_IPV4,
.proto = IPPROTO_UDP,
.table = "filter",
.target = echo_tg4,
.me = THIS_MODULE,
static struct xt_target echo_tg_reg[] __read_mostly = {
{
.name = "ECHO",
.revision = 0,
.family = NFPROTO_IPV6,
.proto = IPPROTO_UDP,
.table = "filter",
.target = echo_tg6,
.me = THIS_MODULE,
},
{
.name = "ECHO",
.revision = 0,
.family = NFPROTO_IPV4,
.proto = IPPROTO_UDP,
.table = "filter",
.target = echo_tg4,
.me = THIS_MODULE,
},
};
static int __init echo_tg_init(void)
{
return xt_register_target(&echo_tg_reg);
return xt_register_targets(echo_tg_reg, ARRAY_SIZE(echo_tg_reg));
}
static void __exit echo_tg_exit(void)
{
return xt_unregister_target(&echo_tg_reg);
return xt_unregister_targets(echo_tg_reg, ARRAY_SIZE(echo_tg_reg));
}
module_init(echo_tg_init);
@@ -140,4 +254,5 @@ module_exit(echo_tg_exit);
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_DESCRIPTION("Xtables: ECHO diagnosis target");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip6t_ECHO");
MODULE_ALIAS("ipt_ECHO");