Basic example af_packet raw server and client

AF_PACKET RAW

• In this program, you are going to learn

• How to create a Socket ?

• How to bind a socket ?

• How to send a data ?

• How to recv a data ?

• How to use socket APIs ?

  • socket

  • bind

  • send

  • recv

Topics in this section,

• program 1: af_packet raw single server and single client : single data transfer

• program 2: af_packet raw single server and single client : multiple data transfer

program 1 : af_packet raw single server and single client : single data transfer

Topics in this section,

• AF_PACKET RAW SOCKET FAQs

• Program1 : Step 1: Sequence Diagram for SERVER.c

• Program1 : Step 2: Program for Server.c

• Program1 : Step 3: Compile and Execute Server.c

• Program1 : Step 4: Sequence Diagram for CLIENT.c

• Program1 : Step 5: Program for Client.c

• Program1 : Step 6: Compile and Execute Client.c

• Summary

program 2 : af_packet raw multiple server and single client : multiple data transfer

Topics in this section,

• AF_PACKET RAW SOCKET FAQs

• Program2 : Step 1: Sequence Diagram for SERVER.c

• Program2 : Step 2: Program for Server.c

• Program2 : Step 3: Compile and Execute Server.c

• Program2 : Step 4: Sequence Diagram for CLIENT.c

• Program2 : Step 5: Program for Client.c

• Program2 : Step 6: Compile and Execute Client.c

• Summary

AF_PACKET RAW SOCKET : FAQs

Let us answer few basic questions in this socket

What does socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)) do?

See Answer

This call creates a raw socket at the data link layer, allowing capturing of all Ethernet frames, including those not destined for the local host.

How can I handle errors when creating a raw socket for packet capturing?

See Answer

Check the return value of the socket function. If it returns -1, use perror to print a descriptive error message.

Are there specific privileges required to create a raw packet socket?

See Answer

Yes, typically, root or superuser privileges are required to create a raw packet socket for security reasons.

What kind of errors can occur when using a raw packet socket?

See Answer

Common errors include permission-related errors (EACCES), socket creation failures (ENOMEM), or invalid arguments (EINVAL).

How do I handle errors when binding a raw packet socket?

See Answer

Check the return value of the bind function. If it returns -1, handle the error by printing a message or taking appropriate corrective action based on the error code.

What is the significance of error code EPERM when dealing with raw packet sockets?

See Answer

EPERM (Operation not permitted) typically indicates insufficient privileges. Ensure the program has the necessary permissions to create raw packet sockets.

How do I handle errors when using recv and send to capture packets and send packets with a raw socket?

See Answer

Check the return value of recv and send. If it returns -1, handle the error by printing a message or taking appropriate corrective action.

Is it important to close the raw packet socket on error?

See Answer

Yes, closing the socket is crucial to release system resources. Always follow error-handling best practices and close sockets on error.

How do I handle timeouts when capturing packets with a raw packet socket?

See Answer

For timeouts, use select or poll in combination with non-blocking mode to wait for data with a specified timeout.

Is it possible to capture packets on a specific network interface with a raw packet socket?

See Answer

Yes, use the bind function to associate the raw packet socket with a specific network interface.

How do I handle errors related to socket file descriptor management?

See Answer

When closing sockets, check for errors using close. Handle errors by printing messages or taking corrective actions.

Program1 : Step 1: Sequence Diagram for SERVER.c

Program1 : Step 2: Program for Server.c

• There are many functions used in socket. We can classify those functions based on functionalities.

  • Create Socket

  • Bind Socket

  • Recv data_packet

  • Close socket

• socket() is used to create a new socket. For example,

raw_socket = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));

• bind() is used to associate the socket with a specific address and port. For example,

ret = bind(raw_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

• recv is used in network programming to receive data from a connected socket. For example,

ret = recv(raw_socket, buffer, BUFFER_SIZE, 0);

• close is used to close the socket To free up system resources associated with the socket. For example,

(void)close(raw_socket);

• See the full program below,

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netpacket/packet.h>
#include <arpa/inet.h>
#include <net/ethernet.h>
#include <signal.h>
#include <net/if.h>

#define BUFFER_SIZE 1500

int main() 
{
  int raw_socket;
  int ret;
  struct sockaddr_ll 
  server_addr;
  char buffer[BUFFER_SIZE];

  raw_socket = socket(AF_PACKET, 
               SOCK_RAW, 
               htons(ETH_P_ALL));

  if (raw_socket < 0) {
    perror("socket");
    return -1;
  }

  memset(&server_addr, 0, 
  sizeof(server_addr));
  server_addr.sll_family = AF_PACKET;
  server_addr.sll_protocol =
  htons(ETH_P_ALL);
  server_addr.sll_ifindex = 
  if_nametoindex("lo");
  
  ret = bind(raw_socket, 
  (struct sockaddr *)&server_addr, 
  sizeof(server_addr));
 
  if (ret < 0) {
    perror("bind");
    (void)close(raw_socket);
    return -2;
  }

  ret = recv(raw_socket, 
  buffer, BUFFER_SIZE, 0);
  
  if (ret < 0) {
    perror("recv");
    (void)close(raw_socket);
    return -3;
  } else {
    printf("recevied = %s\n", 
    buffer);
  }

  (void)close(raw_socket);

  return 0;
}

Program1 : Step 3: Compile and Execute Server.c

$ gcc -o server server.c

$ sudo ./server

recevied = HI

Program1 : Step 4: Sequence Diagram for CLIENT.c

Program1 : Step 5: Program for Client.c

• There are many functions used in socket. We can classify those functions based on functionalities.

  • Create Socket

  • Bind Socket

  • Send data_packet

  • Close socket

• socket is used to create a new socket. For example,

raw_socket = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));

• bind() is used to associate the socket with a specific address and port. For example,

ret = bind(raw_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

• send is used in network programming to send data over a connected socket. For example,

ret = send(raw_socket, buffer, BUFFER_SIZE, 0);

• close is used to close the socket To free up system resources associated with the socket. For example,

(void)close(raw_socket);

• See the full program below,

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include <signal.h>
#include <net/if.h>

#define BUFFER_SIZE 1500

int main(void) 
{
  int raw_socket;
  int ret;
  struct sockaddr_ll 
  server_addr;
  char buffer[BUFFER_SIZE];

  raw_socket = socket(AF_PACKET, 
               SOCK_RAW, 
               htons(ETH_P_ALL));

  if (raw_socket < 0) {
    perror("socket");
    return -1;
  }

  memset(&server_addr, 0, 
  sizeof(server_addr));
  server_addr.sll_family = AF_PACKET;
  server_addr.sll_protocol = 
  htons(ETH_P_ALL);
  server_addr.sll_ifindex = 
  if_nametoindex("lo");
  
  ret = bind(raw_socket, 
  (struct sockaddr *)&server_addr, 
  sizeof(server_addr));
 
  if (ret < 0) {
    perror("bind");
    (void)close(raw_socket);
    return -2;
  }

  sprintf(buffer, "%s", "HI");
  ret = send(raw_socket, 
  buffer, BUFFER_SIZE, 0);
  
  if (ret == -1) {
    perror("send");
    (void)close(raw_socket);
    return -3;
  } else {
    (void)printf("SendingMessage = %s\n",
    buffer);
  }

  (void)close(raw_socket);

  return 0;
}

Program1 : Step 6: Compile and Execute Client.c

$ gcc -o client client.c

$ sudo ./client

SendingMessage = HI

Program2 : Step 1: Sequence Diagram for SERVER.c

Program2 : Step 2: Program for Server.c

• There are many functions used in socket. We can classify those functions based on functionalities.

  • Create Socket

  • Bind Socket

  • Recv data_packet

  • Close socket

• socket() is used to create a new socket. For example,

raw_socket = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));

• bind() is used to associate the socket with a specific address and port. For example,

ret = bind(raw_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

• recv is used in network programming to receive data from a connected socket. For example,

ret = recv(raw_socket, buffer, BUFFER_SIZE, 0);

• close is used to close the socket To free up system resources associated with the socket. For example,

(void)close(raw_socket);

• See the full program below,

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netpacket/packet.h>
#include <arpa/inet.h>
#include <net/ethernet.h>
#include <signal.h>
#include <net/if.h>

#define BUFFER_SIZE 1500
#define NUM_MESSAGES 10

int main() 
{
  int raw_socket;
  int ret, i;
  struct sockaddr_ll 
  server_addr;
  char buffer[BUFFER_SIZE];

  raw_socket = socket(AF_PACKET, 
               SOCK_RAW, 
               htons(ETH_P_ALL));

  if (raw_socket < 0) {
    perror("socket");
    return -1;
  }

  memset(&server_addr, 0, 
  sizeof(server_addr));
  server_addr.sll_family = AF_PACKET;
  server_addr.sll_protocol =
  htons(ETH_P_ALL);
  server_addr.sll_ifindex = 
  if_nametoindex("lo");
  
  ret = bind(raw_socket, 
  (struct sockaddr *)&server_addr, 
  sizeof(server_addr));
 
  if (ret < 0) {
    perror("bind");
    (void)close(raw_socket);
    return -2;
  }

  i = 0;
  while (i < NUM_MESSAGES) {
   ret = recv(raw_socket, 
   buffer, BUFFER_SIZE, 0);
  
   if (ret > 0) {
     printf("recevied = %s\n", 
     buffer);
   } else {
     perror("recv");
     break;
  }
  ++i;
  }

  (void)close(raw_socket);

  return 0;
}

Program2 : Step 3: Compile and Execute Server.c

$ gcc -o server server.c

$ sudo ./server

recevied = hello server!
recevied = hello server!
recevied = hello server!
recevied = hello server!
recevied = hello server!
recevied = hello server!
recevied = hello server!
recevied = hello server!
recevied = hello server!
recevied = hello server!

Program2 : Step 4: Sequence Diagram for CLIENT.c

Program2 : Step 5: Program for Client.c

• There are many functions used in socket. We can classify those functions based on functionalities.

  • Create Socket

  • Bind Socket

  • Send data_packet

  • Close socket

• socket is used to create a new socket. For example,

raw_socket = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));

• bind() is used to associate the socket with a specific address and port. For example,

ret = bind(raw_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

• send is used in network programming to send data over a connected socket. For example,

ret = send(raw_socket, buffer, BUFFER_SIZE, 0);

• close is used to close the socket To free up system resources associated with the socket. For example,

(void)close(raw_socket);

• See the full program below,

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include <signal.h>
#include <net/if.h>

#define BUFFER_SIZE 1500
#define NUM_MESSAGES 10

int main(void) 
{
  int raw_socket;
  int ret, i;
  struct sockaddr_ll 
  server_addr;
  char buffer[BUFFER_SIZE];

  raw_socket = socket(AF_PACKET, 
               SOCK_RAW, 
               htons(ETH_P_ALL));

  if (raw_socket < 0) {
    perror("socket");
    return -1;
  }

  memset(&server_addr, 0, 
  sizeof(server_addr));
  server_addr.sll_family = AF_PACKET;
  server_addr.sll_protocol = 
  htons(ETH_P_ALL);
  server_addr.sll_ifindex = 
  if_nametoindex("lo");
  
  ret = bind(raw_socket, 
  (struct sockaddr *)&server_addr, 
  sizeof(server_addr));
 
  if (ret < 0) {
    perror("bind");
    (void)close(raw_socket);
    return -2;
  }

  i = 0;
  while (i < NUM_MESSAGES) {
   sprintf(buffer, "%s", "hello server!");
   ret = send(raw_socket, 
   buffer, BUFFER_SIZE, 0);
  
   if (ret == -1) {
     perror("send");
     break;
   } else {
     (void)printf("SendingMessage = %s\n",
     buffer);
   }
  ++i;
  }

  (void)close(raw_socket);

  return 0;
}

Program2 : Step 6: Compile and Execute Client.c

$ gcc -o client client.c

$ sudo ./client

SendingMessage = hello server!
SendingMessage = hello server!
SendingMessage = hello server!
SendingMessage = hello server!
SendingMessage = hello server!
SendingMessage = hello server!
SendingMessage = hello server!
SendingMessage = hello server!
SendingMessage = hello server!
SendingMessage = hello server!

Enhanced Socket Flexibility with AF_PACKET and PF_PACKET Domains

Default Domain:

By default, the socket is configured to work in the AF_PACKET domain, handling all types of network data.

Additional Domain Support:

We expand the socket’s capabilities to also function in the PF_PACKET domain, allowing it to operate similarly to AF_PACKET.

Socket Creation:

We set up a network connection point known as a socket using socket(PF_PACKET, SOCK_RAW, IPPROTO_UDP).

Working Scenario:

Despite the change in domain to PF_PACKET, the socket continues to operate the same way, handling general network data.

Enhanced Protocol Flexibility in Socket Configuration

Default Protocol Support:

By default, the socket is configured to support the capture of all Ethernet frames (ETH_P_ALL protocol).

Additional Protocol:

The socket is designed to seamlessly support an additional protocol, namely ETH_P_PAE.

Socket Creation:

A socket is created using the socket(AF_PACKET, SOCK_RAW, htons(ETH_P_PAE)) call.

Working Scenario:

Despite the change in protocol to ETH_P_PAE, the overall working scenario of the socket remains consistent.

Summary

Socket API	Learning
socket	Create a new socket
bind	Associate the socket with a specific address and port
recv	Receive data from a connected socket.
send	Send data over a connected socket.

See Also

• Previous topic

  • // TODO ipv6_raw_af_inet6_raw

• Current topic

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• Next topic

  • af_packet raw server client program with Select system call

• Other socket

  • raw_af_packet_tcp_htons_ETH_P_ALL

  • raw_af_packet_udp_htons_ETH_P_ALL

• Other IPCs

  • Message_queues

  • NamedPipes

  • Netlink

  • Shared_Memory

  • Shared_Memory_2_FDS

  • SocketPair

  • Timerfd