Re: Cannot compile my Xtables module

[Vishal Thanki <vishalthanki@xxxxxxxxx>]

There should not be "st_mtdtor" in line 102, it should be "xt_mtdtor" (i 
think). Apart from there, I suggest you use proper typecast when you 
dereferenct void *. For example, in line 80, you should assign 
"par->matchinfo" to "info"  with proper typecasting (of type struct 
xt_ipaddr_mtinfo *). Hope that helps.

Vishal
Bartek Dolewski wrote:
> Hi there,
> I guess this is more "c programming trouble" than kernel code but
> maybe I`m wrong.
> I`ve started with Netfilter/Xtables stuff so I write below code using
> some resources. When I type "make" I can see these error messages:
>
> LD      /media/ubuntu/home/bartek/Moduły/iptables/built-in.o
>   CC [M]  /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.o
> In file included from
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:1:
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.h:32: warning:
> ‘struct xt_mtdtor’ declared inside parameter list
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.h:32: warning: its
> scope is only this definition or declaration, which is probably not
> what you want
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:13: warning:
> initialization from incompatible pointer type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c: In function
> ‘ipaddr_mt’:
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:59: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:59: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:59: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:59: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:59: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:59: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:59: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:59: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:59: warning: too
> many arguments for format
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:61: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:62: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:62: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:68: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:69: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:69: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c: In function
> ‘ipaddr_mt_check’:
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:87: error:
> expected ‘)’ before ‘{’ token
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:98: error:
> expected expression before ‘}’ token
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c: At top level:
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:100: warning:
> ‘struct st_mtdtor’ declared inside parameter list
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:100: error:
> conflicting types for ‘ipaddr_mt_destroy’
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.h:32: error:
> previous declaration of ‘ipaddr_mt_destroy’ washere
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c: In function
> ‘ipaddr_mt_destroy’:
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:102: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c: In function ‘ipaddr_mt6’:
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:119: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:119: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:119: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:119: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:119: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:119: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:119: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:119: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:119: warning:
> too many arguments for format
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:121: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:122: error:
> implicit declaration of function ‘ipv6_addr_cmp’
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:122: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:122: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:128: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:129: error:
> dereferencing pointer to incomplete type
> /media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.c:129: error:
> dereferencing pointer to incomplete type
> make[2]: *** [/media/ubuntu/home/bartek/Moduły/iptables/xt_ipaddr.o] Error 1
> make[1]: *** [_module_/media/ubuntu/home/bartek/Moduły/iptables] Error 2
> make[1]: Leaving directory `/usr/src/linux-2.6.28-gentoo-r4'
> make: *** [all] Error 2
>
> In my opinion everything is ok with code, i just can`t find any bugs.
> There is my source code
> /********* xt_ipaddr.c **********/
> #include "xt_ipaddr.h"
>
> /*MODULE_LICENSE("GPL"); */
>
>
>
> static struct xt_match ipaddr_mt4_reg  = {
> 		.name 		= "ipaddr",
> 		.revision	= 0,
> 		.family		= NFPROTO_IPV4,
> 		.match		= ipaddr_mt,
> 		.checkentry	= ipaddr_mt_check,
> 		.destroy	= ipaddr_mt_destroy,
> 		.matchsize	= XT_ALIGN(sizeof(struct xt_ipaddr_mtinfo)),
> 		.me		= THIS_MODULE,
> };
>
> static struct xt_match ipaddr_mt6_reg  = {
> 		.name		= "ipaddr",
> 		.revision	= 0,
> 		.family		= NFPROTO_IPV6,
> 		.match		= ipaddr_mt6,
> 		.matchsize	= XT_ALIGN(sizeof(struct xt_ipaddr_mtinfo)),
> 		.me		= THIS_MODULE,
> };
>
> static int __init ipaddr_mt_init(void)
> {
> 	int ret;
> 	ret = xt_register_match(&ipaddr_mt4_reg);
> 	if(ret < 0)
> 		return ret;
>
> 	ret = xt_register_match(&ipaddr_mt6_reg);
> 	if(ret < 0) {
> 		xt_unregister_match(&ipaddr_mt4_reg);
> 		return ret;
> 	}
> 	return 0;
> }
>
> static void __exit ipaddr_mt_exit(void)
> {
> 	xt_unregister_match(&ipaddr_mt4_reg);
> }
>
> static bool ipaddr_mt(const struct sk_buff* skb,
> 		      const struct xt_match_param* par)
> {
> 	const struct xt_ipadr_mtinfo* info = par->matchinfo;
> 	const struct iphdr* iph = ip_hdr(skb);
>
> 	printk(KERN_INFO
> 		"xt_ipaddr: IN=%s OUT=%s"
> 		"SRC=" NIPQUAD_FMT " DST=" NIPQUAD_FMT "\n",
> 		(par->in  != NULL) ? par->in->name : "",
> 		(par->out != NULL) ? par->out->name : "",
> 		NIPQUAD(iph->saddr), NIPQUAD(iph->daddr),
> 		NIPQUAD(info->src),  NIPQUAD(info->dst));
>
> 	if(info->flags & XT_IPADDR_SRC)
> 		if( (iph->saddr != info->src.ip) ^ !!(info->flags & XT_IPADDR_SRC_INV) )
> 		{
> 			printk(KERN_NOTICE "src IP - no match\n");
> 			return false;
> 		}
>
> 	if(info->flags & XT_IPADDR_DST)
> 		if( (iph->daddr != info->dst.ip) ^ !!(info->flags & XT_IPADDR_DST_INV) )
> 		{
> 			printk(KERN_NOTICE "dst IP - no match\n");
> 			return false;
> 		}
> 	return true;
>
> }
>
> static bool ipaddr_mt_check(const struct xt_mtchk_param* par)
> {
> 	const struct xt_ipaddr_mtinfo* info = par->matchinfo;
>
> 	printk(KERN_INFO "xt_ipaddr: Added a rule with -m ipaddr in"
> 			 "the %s table; this rule is reachable through"
> 			 "hooks 0x%x\n",
> 			 par->table, par->hook_mask);
>
> 		if( !(info->flags & (XT_IPADDR_SRC | XT_IPADDR_DST) ) {
> 			printk(KERN_INFO "xt_ipaddr: testing for nothing\n");
> 			return false;
> 		}
>
> 	if(ntohl(info->src.ip) == 0xDEADBEEF) {
> 		printk(KERN_INFO "xt_ipaddr: I just thought I do not"
> 				 "wanto to let you match on 222.173.190.239\n");
> 		return false;
> 	}
>
> }
>
> static void ipaddr_mt_destroy(const struct st_mtdtor *par)
> {
> 	const struct xt_ipaddr_mtinfo *info = par->matchinfo;
> 	printk(KERN_INFO "Test for address %081X removed\n", info->src.ip);
> }
>
> /* here are routines for IPv6 */
>
> static bool ipaddr_mt6(const struct sk_buff* skb,  const struct
> xt_match_param* par)
> {
> 	const struct xt_ipadr_mtinfo *info = par->matchinfo;
> 	const struct ipv6hdr* iph = ipv6_hdr(skb);
>
> 	printk(KERN_INFO
> 		"xt_ipaddr: IN=%s OUT=%s"
> 		"SRC=" NIPQUAD_FMT " DST=" NIPQUAD_FMT "\n",
> 		(par->in  != NULL) ? par->in->name : "",
> 		(par->out != NULL) ? par->out->name : "",
> 		NIPQUAD(iph->saddr), NIPQUAD(iph->daddr),
> 		NIPQUAD(info->src),  NIPQUAD(info->dst));
>
> 	if(info->flags & XT_IPADDR_SRC)
> 		if((ipv6_addr_cmp(&iph->saddr, &info->src.in6) != 0) ^
> !!(info->flags & XT_IPADDR_SRC_INV) )
> 		{
> 			printk(KERN_NOTICE "src IP - no match\n");
> 			return false;
> 		}
>
> 	if(info->flags & XT_IPADDR_DST)
> 		if((ipv6_addr_cmp(&iph->daddr, &info->dst.in6) != 0) ^
> !!(info->flags & XT_IPADDR_DST_INV) )
> 		{
> 			printk(KERN_NOTICE "drc IP - no match\n");
> 			return false;
> 		}
> 	return true;
>
> }
>
> module_init(ipaddr_mt_init);
> module_exit(ipaddr_mt_exit);
>
> /********** xt_ipaddr.h *************/
> #ifndef _LINUX_NETFILTER_XT_IPADDR_H
> #define _LINUX_NETFILTER_XT_IPADDR_H
>
> #include <linux/module.h>
> #include <linux/init.h>
> #include <linux/kernel.h>
> #include <linux/netfilter.h>
> #include <linux/inet.h>
> #include <linux/ip.h>
> #include <linux/ipv6.h>
> #include <linux/netfilter/x_tables.h>
> #include <net/dsfield.h>
> #include <linux/skbuff.h>
>
>
>
> enum {
> 	XT_IPADDR_SRC	  = 1 << 0,
> 	XT_IPADDR_DST	  = 1 << 1,
> 	XT_IPADDR_SRC_INV = 1 << 2,
> 	XT_IPADDR_DST_INV = 1 << 3,
> };
>
> struct xt_ipaddr_mtinfo {
> 	union nf_inet_addr src, dst;
> 	__u8 flags;
> };
>
> /*declarations of functions */
> static bool ipaddr_mt(const struct sk_buff* skb, const struct
> xt_match_param* par);
> static bool ipaddr_mt_check(const struct xt_mtchk_param* par);
> static void ipaddr_mt_destroy(const struct xt_mtdtor* par);
>
> /* IPv6 */
> static bool ipaddr_mt6(const struct sk_buff* skb, const struct
> xt_match_param* par);
>
> #endif /* _LINUX_NETFILTER_XT_IPADDR_H */
>
>
>   


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