VIDEOS 》 Linux Kernel /proc Interface

Download this episode my entire kernel module sample code, make file, clean script HERE. And here is the same source code for a quick reference.

/* proc_example.c
 * Author: Kiran Kankipati
 * Updated: 22-feb-2017
 */
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/module.h> 
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/skbuff.h>  
#include <linux/udp.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/icmp.h>
#include <linux/proc_fs.h>
#include <linux/netlink.h>
#include <linux/mroute.h>
#include <net/checksum.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/route.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/arp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/inetpeer.h>
#include <net/protocol.h>
#include <net/flow.h>
#include <asm/types.h>

struct proc_dir_entry *tlc_proc_a;

static ssize_t tlc_proc_a_read(struct file *fp, char *buf, size_t len, loff_t * off)
{	static int finished=0; if(finished) {finished=0;return 0;} finished=1;
	//int abc=100;
	//strcpy(buf, "abc: %d\n", abc);
	//sprintf(buf, "abc: %d\n", abc);
	memset(buf,0xaa,10);
	//return strlen(buf);
	return 10;
}

static struct file_operations tlc_proc_a_fops = { .owner=THIS_MODULE, .read=tlc_proc_a_read, };

static int hello_init(void)
{
 	tlc_proc_a = proc_create( "tlc_proc_a", 0444, NULL, &tlc_proc_a_fops); 
 	if(tlc_proc_a==NULL) {	printk(KERN_ALERT "Error: Could not initialize %s\n", "tlc_proc_a"); }
	
	return 0;
}

static void hello_exit(void) 
{  remove_proc_entry("tlc_proc_a", NULL);
}

module_init(hello_init);
module_exit(hello_exit);

Download this episode my entire kernel module sample code, make file, clean script HERE. And here is the same source code for a quick reference.

/* proc_example.c - write /proc file
 * Author: Kiran Kankipati
 * Updated: 23-feb-2017
 */
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/module.h> 
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/skbuff.h>  
#include <linux/udp.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/icmp.h>
#include <linux/proc_fs.h>
#include <linux/netlink.h>
#include <linux/mroute.h>
#include <net/checksum.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/route.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/arp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/inetpeer.h>
#include <net/protocol.h>
#include <net/flow.h>
#include <asm/types.h>

struct proc_dir_entry *tlc_proc_a;

int abc=100;

#define PROCFS_MAX_SIZE 30
char proc_buf[PROCFS_MAX_SIZE];

static ssize_t tlc_proc_a_write(struct file *fp, const char *buf, size_t len, loff_t * off)
{	if(len > PROCFS_MAX_SIZE) { return -EFAULT; }
   if(copy_from_user(proc_buf, buf, len)) { return -EFAULT; }

	abc=simple_strtoul(proc_buf,NULL,10);
	return len;
}


static ssize_t tlc_proc_a_read(struct file *fp, char *buf, size_t len, loff_t * off)
{	static int finished=0; if(finished) {finished=0;return 0;} finished=1;
	
	sprintf(buf, "abc: %d\n", abc);
	return strlen(buf);
}

static struct file_operations tlc_proc_a_fops = { .owner=THIS_MODULE, .read=tlc_proc_a_read, .write=tlc_proc_a_write, };

static int hello_init(void)
{
 	tlc_proc_a = proc_create( "tlc_proc_a", 0666, NULL, &tlc_proc_a_fops); 
 	if(tlc_proc_a==NULL) {	printk(KERN_ALERT "Error: Could not initialize %s\n", "tlc_proc_a"); }
	
	return 0;
}

static void hello_exit(void) 
{  remove_proc_entry("tlc_proc_a", NULL);
}

module_init(hello_init);
module_exit(hello_exit);

Download this episode my entire kernel module sample code, make file, clean script HERE. And here is the same source code for a quick reference.

/* proc_example.c - /proc directory
 * Author: Kiran Kankipati
 * Updated: 24-feb-2017
 */
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/module.h> 
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/skbuff.h>  
#include <linux/udp.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/icmp.h>
#include <linux/proc_fs.h>
#include <linux/netlink.h>
#include <linux/mroute.h>
#include <net/checksum.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/route.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/arp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/inetpeer.h>
#include <net/protocol.h>
#include <net/flow.h>
#include <asm/types.h>

struct proc_dir_entry *tlc_proc_dir;
struct proc_dir_entry *tlc_proc_a;

int abc=100;

#define PROCFS_MAX_SIZE 30
char proc_buf[PROCFS_MAX_SIZE];

static ssize_t tlc_proc_a_write(struct file *fp, const char *buf, size_t len, loff_t * off)
{	if(len > PROCFS_MAX_SIZE) { return -EFAULT; }
   if(copy_from_user(proc_buf, buf, len)) { return -EFAULT; }

	abc=simple_strtoul(proc_buf,NULL,10);
	return len;
}


static ssize_t tlc_proc_a_read(struct file *fp, char *buf, size_t len, loff_t * off)
{	static int finished=0; if(finished) {finished=0;return 0;} finished=1;
	
	sprintf(buf, "abc: %d\n", abc);
	return strlen(buf);
}

static struct file_operations tlc_proc_a_fops = { .owner=THIS_MODULE, .read=tlc_proc_a_read, .write=tlc_proc_a_write, };

static int hello_init(void)
{
	tlc_proc_dir=proc_mkdir( "tlc_proc_dir", NULL);
 	tlc_proc_a = proc_create( "tlc_proc_a", 0666, tlc_proc_dir, &tlc_proc_a_fops); 
 	if(tlc_proc_a==NULL) {	printk(KERN_ALERT "Error: Could not initialize %s\n", "tlc_proc_a"); }
	
	return 0;
}

static void hello_exit(void) 
{  remove_proc_entry("tlc_proc_a", NULL);
}

module_init(hello_init);
module_exit(hello_exit);

Download this episode my entire kernel module sample code, make file, clean script HERE. And here is the same source code for a quick reference.

/* proc_example.c - /proc access to drop pkts
 * Author: Kiran Kankipati
 * Updated: 25-feb-2017
 */
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/module.h> 
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/skbuff.h>  
#include <linux/udp.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/icmp.h>
#include <linux/proc_fs.h>
#include <linux/netlink.h>
#include <linux/mroute.h>
#include <net/checksum.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/route.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/arp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/inetpeer.h>
#include <net/protocol.h>
#include <net/flow.h>
#include <asm/types.h>

struct proc_dir_entry *tlc_proc_a;

int drop_pkts=0;

#define PROCFS_MAX_SIZE 30
char proc_buf[PROCFS_MAX_SIZE];

static ssize_t tlc_proc_a_write(struct file *fp, const char *buf, size_t len, loff_t * off)
{	int val=0;
	if(len > PROCFS_MAX_SIZE) { return -EFAULT; }
   if(copy_from_user(proc_buf, buf, len)) { return -EFAULT; }

	val=simple_strtoul(proc_buf,NULL,10); if(val==0 || val==1) { drop_pkts=val; }
	return len;
}


static ssize_t tlc_proc_a_read(struct file *fp, char *buf, size_t len, loff_t * off)
{	static int finished=0; if(finished) {finished=0;return 0;} finished=1;
	
	if(drop_pkts) { sprintf(buf, "drop_pkts: true\n"); } else { sprintf(buf, "drop_pkts: false\n"); }
	return strlen(buf);
}

static struct file_operations tlc_proc_a_fops = { .owner=THIS_MODULE, .read=tlc_proc_a_read, .write=tlc_proc_a_write, };

static struct nf_hook_ops nfho_pre_routing;

unsigned int pre_routing_hook_func(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
{
	if(drop_pkts) { return NF_DROP; }
	return NF_ACCEPT;
}

static int hello_init(void)
{
 	tlc_proc_a = proc_create( "tlc_proc_a", 0666, NULL, &tlc_proc_a_fops); 
 	if(tlc_proc_a==NULL) {	printk(KERN_ALERT "Error: Could not initialize %s\n", "tlc_proc_a"); goto hello_init_end; }
 	
 	//Packet RX
	nfho_pre_routing.hook = pre_routing_hook_func;
	nfho_pre_routing.hooknum = NF_INET_PRE_ROUTING;
	nfho_pre_routing.pf = PF_INET;
	nfho_pre_routing.priority = NF_IP_PRI_FIRST;
	nf_register_hook(&nfho_pre_routing);

hello_init_end:	
	return 0;
}

static void hello_exit(void) 
{  remove_proc_entry("tlc_proc_a", NULL);
	nf_unregister_hook(&nfho_pre_routing);
}

module_init(hello_init);
module_exit(hello_exit);

Download my sample C-code(with compile script) discussed in this video episode HERE.

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