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Q.8 Explain what can RAW sockets do and system calls used for creation.hiw raw socket handling packets during I/O operations

Answer.

RAW sockets allow for direct access to network communication at the protocol level. They bypass the normal TCP/IP stack and provide the ability to craft and interpret packets at a low level. This means you can create custom protocols, implement network utilities like traceroute or ping, or perform network analysis tasks.

System calls used for creation and handling of RAW sockets typically include:

socket(): Used to create a RAW socket. The socket type SOCK_RAW is specified to indicate that it’s a RAW socket.
bind(): Optionally used to bind the RAW socket to a specific network interface.
sendto() and recvfrom(): Used for sending and receiving packets respectively. These system calls allow you to specify the destination and source addresses of the packet.
setsockopt(): Used to set options for the socket, such as specifying the protocol (e.g., IPPROTO_TCP, IPPROTO_UDP).

When handling packets during I/O operations:

Receiving Packets: When a packet is received, it’s typically read from the network interface into a buffer in the kernel space. The application can then use the recvfrom() system call to retrieve the packet from the buffer.
Sending Packets: When an application wants to send a packet, it writes the packet data into a buffer in the kernel space. Then, the sendto() system call is used to send the packet out through the network interface.
Packet Filtering and Processing: Applications can filter and process packets as needed. For example, a packet capture tool might capture all incoming packets and analyze them for specific patterns or protocols.

Overall, RAW sockets provide a powerful mechanism for network programming, enabling developers to interact with the network at a very low level. However, they also require careful handling to avoid security vulnerabilities and system instability

Q.7) A Deadlock is a situation where two or more blocked because each is waiting on the other processes to complete some action. The two processes shown Process X 1. Open FIFO A for reading 2. Open FIFO B for writing blocks Process Y 1. Open FIFO B for reading 2. Open FIFO A for writing Explain the steps to resolve the deadlock between processes opening two FIFO’s.

Answer.

To resolve the deadlock between processes opening two FIFOs (named FIFO A and FIFO B), you can employ various strategies. One common approach is to ensure that processes always acquire resources (in this case, FIFOs) in a consistent order. Here are the steps to resolve the deadlock in this scenario:

1. Analyze and Identify Deadlock: First, confirm that a deadlock exists by observing that both processes are blocked while waiting for resources held by the other.
2. Resource Allocation Order: Establish a consistent order for acquiring resources. In this case, let’s decide that FIFO A will always be acquired before FIFO B.
3. Modify Process Y: Adjust the sequence of resource acquisition in Process Y to ensure it follows the defined order. So, modify Process Y as follows:
   Process Y
   1. Open FIFO A for writing
   2. Open FIFO B for reading
4. Modify Process X: Similarly, update Process X to maintain consistency in resource acquisition:
   Process X
   1. Open FIFO A for reading
   2. Open FIFO B for writing
5. Implement Resource Locking Mechanism: To prevent conflicts and ensure that resources are accessed exclusively, implement a locking mechanism. This mechanism ensures that a process cannot access a resource if it’s already being used by another process.
6. Error Handling: Implement error handling mechanisms in both processes to handle situations where the resources are unavailable or inaccessible due to contention.

By following these steps, you can ensure that both processes consistently acquire resources in the same order, thereby preventing deadlocks from occurring. Additionally, implementing a locking mechanism helps manage resource access efficiently and handle potential conflicts.

Q.4) A Sports equipment manufacturing company has different hardware architecture in their network. How will you handle the data when passing these values across a network that stores the bytes of a multi byte integer in different orders?
a) Represent you your solution explaining the different architectures available with a diagram.
b) List the functions to convert these values to network byte order before storing them in socket address structures.

Answer.

a) Different Hardware Architectures:

1. Big-Endian: In this architecture, the most significant byte (MSB) is stored at the smallest memory address, and the least significant byte (LSB) is stored at the largest memory address. It’s like reading from left to right, where the leftmost digit holds the most weight.
2. Little-Endian: Here, the least significant byte (LSB) is stored at the smallest memory address, and the most significant byte (MSB) is stored at the largest memory address. It’s akin to reading from right to left, where the rightmost digit holds the most weight.

b) Functions to Convert Values to Network Byte Order:

In C/C++, you would typically use functions from the arpa/inet.h library to convert values to network byte order (Big-Endian) before storing them in socket address structures. Here are some of the key functions:

1. htons() – Convert a 16-bit host short integer to network byte order.
2. htonl() – Convert a 32-bit host long integer to network byte order.
3. ntohs() – Convert a 16-bit network short integer to host byte order.
4. ntohl() – Convert a 32-bit network long integer to host byte order.

These functions help ensure that data is properly represented in network byte order regardless of the underlying architecture.

Q.3) In the process of user and group information retrievals, System library functions allows us to retrieve individual records from the password, shadow password, and group likes, and to scan all of the records in each of these tiles. A client has come up with a requirement to design a program which scans the records from the group file and to write supplement functions which converts the symbolic user and group names into numeric IDs and vice versa

Answer.

To fulfill the requirement of designing a program that scans records from the group file and provides functions to convert symbolic user and group names into numeric IDs and vice versa, you can follow these steps:

1. Read the Group File: Write a function to read the group file and parse its records. The group file is typically located at /etc/group in Unix-like systems.
2. Parse Records: Parse each record from the group file. Each record typically consists of fields separated by colons (:), such as group name, group password (if applicable), group ID, and a list of user IDs.
3. Conversion Functions:
   • Implement a function to convert symbolic group names to numeric group IDs. This function will take a group name as input and return its corresponding numeric group ID.
   • Implement a function to convert numeric group IDs to symbolic group names. This function will take a numeric group ID as input and return its corresponding symbolic group name.
4. Scan Records: Write a function to scan through all records in the group file. This function can utilize the parsing function and can either return all records or process them in some way as required by the client.
5. Integration: Integrate the above components into a cohesive program that fulfills the client’s requirements.

Here’s a simplified Python example to illustrate the process:

def read_group_file(file_path):
with open(file_path, 'r') as file:
return file.readlines()

def parse_group_record(record):
fields = record.strip().split(':')
return {
'name': fields[0],
'password': fields[1],
'gid': int(fields[2]),
'users': fields[3].split(',') if fields[3] else []
}

def symbolic_to_numeric(group_name, group_records):
for record in group_records:
if record['name'] == group_name:
return record['gid']
return None

def numeric_to_symbolic(group_id, group_records):
for record in group_records:
if record['gid'] == group_id:
return record['name']
return None

def scan_group_records(file_path):
group_records = []
lines = read_group_file(file_path)
for line in lines:
group_records.append(parse_group_record(line))
return group_records

# Example usage
group_file_path = '/etc/group'
group_records = scan_group_records(group_file_path)
print(symbolic_to_numeric('sudo', group_records)) # Example: symbolic to numeric
print(numeric_to_symbolic(1001, group_records)) # Example: numeric to symbolic

Q.2) a program to create a TCP client server socket It server sock program which acts like online dictionary After successful connection the client wil akt meaning of a certain work, if available with server it will return the meaning to the client. This should be continued il client sends a tye message
Two separate programs must be written one for client and another for server

Answer.

Q.1) Application developer has installed web server in his Linux development machine. To test the web application, developer wants to know local IP address of the machine Write a C Write a C program to find out the hostname of the local system and find local host IP address

Answers.

You can use the gethostname() and getaddrinfo() functions in C to achieve this. Below is a simple C program that retrieves the hostname of the local system and then finds its corresponding IP address:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>

int main() {
char hostname[256];
struct hostent *host_info;
struct in_addr **addr_list;
int i;

// Get the hostname of the local system
if (gethostname(hostname, sizeof(hostname)) == -1) {
perror("gethostname");
return 1;
}

printf("Hostname: %s\n", hostname);

// Get host information using the hostname
if ((host_info = gethostbyname(hostname)) == NULL) {
herror("gethostbyname");
return 1;
}

// Get the list of IP addresses associated with the hostname
addr_list = (struct in_addr **)host_info->h_addr_list;

// Print all IP addresses
for (i = 0; addr_list[i] != NULL; i++) {
printf("IP Address %d: %s\n", i+1, inet_ntoa(*addr_list[i]));
}

return 0;
}

It will print the hostname of the local system and its corresponding IP addresses.

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