Subject: Re: TCP port firewall controlled by UDP packets

From: Antonin Steinhauser <[email-masked]>
Date: Fri, 12 Aug 2011 17:35:07 +0200

Dne 12.8.2011 02:13, Randy Dunlap napsal(a):
> On Fri, 12 Aug 2011 01:56:09 +0200 Tonda wrote:
>
> Need more patch description&  justification here, as well as
> Signed-off-by:<your name&  email address>
>
>
>    
>> diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
>> --- a/net/ipv4/Kconfig
>> +++ b/net/ipv4/Kconfig
>> @@ -624,3 +624,7 @@
>>   	  on the Internet.
>>
>>   	  If unsure, say N.
>> +
>> +config TCPFIREWALL
>> +	tristate "TCP Firewall controlled by UDP queries"
>> +	depends on m
>>      
> Why buildable only as a loadable module?
>
>    
Because it needs parameter - address of inet_protos table from 
/boot/System_map
>    
>> diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
>> --- a/net/ipv4/Makefile
>> +++ b/net/ipv4/Makefile
>> @@ -51,3 +51,4 @@
>>
>>   obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
>>   		      xfrm4_output.o
>> +obj-$(CONFIG_TCPFIREWALL) += tcpfirewall/
>> diff --git a/net/ipv4/tcpfirewall/Makefile b/net/ipv4/tcpfirewall/Makefile
>> --- a/net/ipv4/tcpfirewall/Makefile
>> +++ b/net/ipv4/tcpfirewall/Makefile
>> @@ -0,0 +1 @@
>> +obj-$(CONFIG_TCPFIREWALL) += tcpfirewall.o
>> diff --git a/net/ipv4/tcpfirewall/tcpfirewall.c b/net/ipv4/tcpfirewall/tcpfirewall.c
>> --- a/net/ipv4/tcpfirewall/tcpfirewall.c
>> +++ b/net/ipv4/tcpfirewall/tcpfirewall.c
>> @@ -0,0 +1,451 @@
>> +#include<linux/module.h>
>> +#include<linux/kernel.h>
>> +#include<linux/init.h>
>> +#include<linux/skbuff.h>
>> +#include<linux/in.h>
>> +#include<linux/if_packet.h>
>> +#include<linux/tcp.h>
>> +#include<linux/udp.h>
>> +#include<net/tcp.h>
>> +#include<net/udp.h>
>> +
>> +struct net_protocol {
>> +	int (*handler)(struct sk_buff *skb);
>> +	void (*err_handler)(struct sk_buff *skb, u32 info);
>> +	int (*gso_send_check)(struct sk_buff *skb);
>> +	struct sk_buff *(*gso_segment)(struct sk_buff *skb,
>> +		u32 features);
>> +	struct sk_buff **(*gro_receive)(struct sk_buff **head,
>> +		struct sk_buff *skb);
>> +	int (*gro_complete)(struct sk_buff *skb);
>> +	unsigned int no_policy:1,
>> +		netns_ok:1;
>> +};
>> +
>> +MODULE_LICENSE("GPL");
>> +
>> +static unsigned long inet_protos = 0x01234567;
>> +
>> +struct net_protocol **_inet_protos;
>> +
>> +module_param(inet_protos, ulong, 0);
>> +
>> +static int *otviraky;
>> +static int *zaviraky;
>> +
>> +static int pocetotviraku;
>> +static int pocetzaviraku;
>> +static int stav;
>> +static int packetcounter;
>> +static int tcpport;
>> +static int open;
>> +static int firewall;
>> +
>> +int (*tcpv4recv) (struct sk_buff *skb);
>> +int (*udprecv) (struct sk_buff *skb);
>> +
>> +int udpcontroller(struct sk_buff *skb)
>>      
> can be static?
>
>    
Yes
>> +{
>> +	const struct udphdr *uh;
>> +
>> +	if (skb->pkt_type != PACKET_HOST) {
>> +		kfree_skb(skb);
>> +		return 0;
>> +	}
>> +
>> +	if (!pskb_may_pull(skb, sizeof(struct tcphdr))) {
>> +		kfree_skb(skb);
>> +		return 0;
>> +	}
>> +
>> +	uh = udp_hdr(skb);
>> +
>> +	if (pocetotviraku == 0)
>> +		return udprecv(skb);
>> +
>> +	if (!open) {
>> +		if (uh->dest == otviraky[stav]) {
>> +			++stav;
>> +			packetcounter = 0;
>> +
>> +			if (stav == pocetotviraku) {
>> +				open = 1;
>> +				stav = 0;
>> +			}
>> +		} else {
>> +			if (packetcounter<= 16) {
>> +				++packetcounter;
>> +				if (packetcounter>  16)
>> +					stav = 0;
>> +			}
>> +		}
>> +	} else {
>> +		if (uh->dest == zaviraky[stav]) {
>> +			++stav;
>> +			packetcounter = 0;
>> +
>> +			if (stav == pocetzaviraku) {
>> +				open = 0;
>> +				stav = 0;
>> +			}
>> +		} else {
>> +			if (packetcounter<= 16) {
>> +				++packetcounter;
>> +				if (packetcounter>  16)
>> +					stav = 0;
>> +			}
>> +		}
>> +	}
>> +
>> +
>> +	return udprecv(skb);
>> +}
>> +
>> +int tcpfirewall(struct sk_buff *skb)
>>      
> can be static?
>
>    
Yes
>> +{
>> +	const struct tcphdr *th;
>> +
>> +	if (skb->pkt_type != PACKET_HOST) {
>> +		kfree_skb(skb);
>> +		return 0;
>> +	}
>> +
>> +	if (!pskb_may_pull(skb, sizeof(struct tcphdr))) {
>> +		kfree_skb(skb);
>> +		return 0;
>> +	}
>> +
>> +	th = tcp_hdr(skb);
>> +
>> +	if (th->dest == tcpport) {
>> +		if (firewall == 1&&  !open) {
>> +			/*tcpv4sendreset(NULL, skb);*/
>> +			kfree_skb(skb);
>> +			return 0;
>> +		}
>> +	}
>> +
>> +	return tcpv4recv(skb);
>> +}
>>      
> [snip]
>
>    
>> +static int __init start(void)
>> +{
>> +	if (inet_protos == 0x01234567) {
>> +		printk(KERN_WARNING "inet_protos parameter was not");
>> +		printk(KERN_WARNING " specified!\nread its value from");
>> +		printk(KERN_WARNING " System_map file file, and insert");
>> +		printk(KERN_WARNING " the module again!\n");
>>      
> Break the printk() calls at newlines, please.
>
>    
OK
>> +		return -1;
>> +	}
>> +
>> +	pocetotviraku = 0;
>> +	pocetzaviraku = 0;
>> +	stav = -1;
>> +	packetcounter = 0;
>> +	tcpport = 0;
>> +	open = 1;
>> +	firewall = 0;
>> +
>> +	memset(&kobj, 0, sizeof(struct kobject));
>> +
>> +	_inet_protos = (struct net_protocol **)inet_protos;
>> +
>> +	kobject_init(&kobj,&khid);
>> +	if (kobject_add(&kobj, NULL, "tcpfirewall")<  0)
>> +		printk(KERN_ERR "kobject_add failed");
>> +
>>      
> All of these kobject_add() and sysfs_create_file() failures are not
> fatal errors?
>
>    
I do not know, whether collision of kobject names is fatal or not.
>> +	if (sysfs_create_file(&kobj,&fw)<  0)
>> +		printk(KERN_ERR "sysfs_create_file failed");
>> +	if (sysfs_create_file(&kobj,&opn)<  0)
>> +		printk(KERN_ERR "sysfs_create_file failed");
>> +	if (sysfs_create_file(&kobj,&tcpp)<  0)
>> +		printk(KERN_ERR "sysfs_create_file failed");
>> +	if (sysfs_create_file(&kobj,&openers)<  0)
>> +		printk(KERN_ERR "sysfs_create_file failed");
>> +	if (sysfs_create_file(&kobj,&closers)<  0)
>> +		printk(KERN_ERR "sysfs_create_file failed");
>> +	if (sysfs_create_file(&kobj,&stat)<  0)
>> +		printk(KERN_ERR "sysfs_create_file failed");
>> +	if (sysfs_create_file(&kobj,&counte)<  0)
>> +		printk(KERN_ERR "sysfs_create_file failed");
>> +
>> +	zalohatcp = _inet_protos[IPPROTO_TCP];
>> +	zalohaudp = _inet_protos[IPPROTO_UDP];
>> +	mytcp = *zalohatcp;
>> +	myudp = *zalohaudp;
>> +	tcpv4recv = mytcp.handler;
>> +	udprecv = myudp.handler;
>> +	mytcp.handler = tcpfirewall;
>> +	myudp.handler = udpcontroller;
>> +	_inet_protos[IPPROTO_TCP] =&mytcp;
>> +	_inet_protos[IPPROTO_UDP] =&myudp;
>> +	return 0;
>> +}
>> +
>> +static void konec(void)
>> +{
>> +	_inet_protos[IPPROTO_TCP] = zalohatcp;
>> +	_inet_protos[IPPROTO_UDP] = zalohaudp;
>> +
>> +	if (pocetotviraku)
>> +		kfree(otviraky);
>> +	if (pocetzaviraku)
>> +		kfree(zaviraky);
>> +
>> +	kobject_del(&kobj);
>> +}
>> +
>> +module_init(start);
>> +module_exit(konec);
>> --
>>      
> Some of the function&  variable names confuse me.
>
>
>    
I renamed them in the second version.
Should I resend the corrected patch again?
> ---
> ~Randy
> *** Remember to use Documentation/SubmitChecklist when testing your code ***
>
>