struct addrinfo, getaddrinfo and

recent functions usage added (as in beej's network programming guide)

Beej_network_programs/Makefile

@@ -0,0 +1,19 @@
+
+
+.PHONY: clean
+
+T1= showip
+T2= client
+TARGETS= $(T1) $(T2) 
+
+all: $(TARGETS)
+
+
+$(T1): $(T1).c
+	gcc $< -o $@
+
+$(T2): $(T2).c
+	gcc $< -o $@
+
+clean:
+	rm $(TARGETS)

Beej_network_programs/client.c

@@ -0,0 +1,189 @@
+// Author : Abhinav Thakur
+// Email  : [email protected]
+
+/* 
+
+In /usr/include/netdb.h
+
+struct addrinfo
+{
+  int ai_flags;                 // Input flags.  
+  int ai_family;                // Protocol family for socket.  
+  int ai_socktype;              // Socket type.  
+  int ai_protocol;              // Protocol for socket.  
+  socklen_t ai_addrlen;         // Length of socket address. 
+  struct sockaddr *ai_addr;     // Socket address for socket.  
+  char *ai_canonname;           // Canonical name for service location.  
+  struct addrinfo *ai_next;     // Pointer to next in list.  
+};
+
+
+
+In /usr/include/netinet/in.h
+
+// for IPv4
+struct sockaddr_in
+{
+    __SOCKADDR_COMMON (sin_);
+    in_port_t sin_port;             // Port number.  
+    struct in_addr sin_addr;        // Internet address.  
+
+    // Pad to size of `struct sockaddr'.  
+    unsigned char sin_zero[sizeof (struct sockaddr) -
+               __SOCKADDR_COMMON_SIZE -
+               sizeof (in_port_t) -
+               sizeof (struct in_addr)];
+};
+
+// Ditto, for IPv6.  
+struct sockaddr_in6
+{
+    __SOCKADDR_COMMON (sin6_);
+    in_port_t sin6_port;            // Transport layer port #
+    uint32_t sin6_flowinfo;         // IPv6 flow information 
+    struct in6_addr sin6_addr;      // IPv6 address 
+    uint32_t sin6_scope_id;         // IPv6 scope-id 
+};
+
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <netdb.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+#define FAMILY AF_UNSPEC
+#define SOCKTYPE SOCK_STREAM
+#define MAXSIZE 13
+
+int main(int argc, char *argv[])
+{
+	struct addrinfo hints, *server_info = NULL;
+	struct addrinfo *parser = NULL;
+	int sockfd = 0, status = 0;
+
+
+	// check for the command line args
+	if (argc != 3)
+	{
+		fprintf(stderr, "Usage: %s <HOSTNAME> <PORT>\n", argv[0]);
+		exit(0x10);	
+	}
+
+	// fill in the server config to connect to and get them stored in struct addrinfo *server_info
+	memset(&hints, 0, sizeof hints);
+	hints.ai_family = FAMILY;
+	hints.ai_socktype = SOCKTYPE;
+
+	status = getaddrinfo(argv[1], argv[2], &hints, &server_info);
+	if (status != 0x0)
+	{
+		fprintf(stderr, "getaddrinfo: ");
+		exit(0x11);
+	}
+
+	// Parse through the search results (Linked list) and connect to the first we can
+	for (parser = server_info; parser != NULL; parser = parser->ai_next)
+	{
+		// try creating a socket
+		sockfd = socket(parser->ai_family, parser->ai_socktype, parser->ai_protocol);
+		if (sockfd == -1)
+		{
+			perror("socket: ");
+			continue;					// try creating a socket through next node
+		}
+
+		// try connecting to server
+		status = connect(sockfd, parser->ai_addr, parser->ai_addrlen);
+		if (status == -1)
+		{
+			perror("connect: ");
+			continue;					// Try through the next node in linked list
+		}
+
+		break;
+	}
+
+
+	if (parser == NULL)
+	{
+		fprintf(stderr, "client: failed to conect after parser reached NULL (end of linked list)\n");
+		exit(0x12);
+	}
+
+	void *raw_ip;
+	char ip_string[INET6_ADDRSTRLEN];
+
+
+	// If IPv4 is IPv4, convert from network to presentation form
+	if (parser->ai_addr->sa_family == AF_INET)
+	{
+		raw_ip = &( ((struct sockaddr_in *)(parser->ai_addr))->sin_addr );
+		inet_ntop(parser->ai_family, raw_ip , ip_string, sizeof ip_string);
+		printf("Client: connected to %s\n", ip_string);
+	}
+
+	// If family is IPv6, convert from network to presentation form
+	else 
+	{
+		raw_ip = &( ((struct sockaddr_in6 *)(parser->ai_addr))->sin6_addr );
+		inet_ntop(parser->ai_family, raw_ip, ip_string, sizeof ip_string);
+		printf("Client: connected to %s\n", ip_string);
+	}
+
+	freeaddrinfo(server_info);
+
+
+	char buffer[16];
+	unsigned int *pointer = NULL, *pointerx = NULL;
+	unsigned int bytes_recieved = 0, bytes_sent = 0;
+	unsigned int counter = 0, counterx = 0;
+	unsigned int return_value = 0;
+	uint64_t sum = 0; 
+
+
+
+	// recieving 16 bytes(4 unsingned ints) in host byte order from server
+	bytes_recieved = recv(sockfd, buffer, 16, 0x0);
+
+	printf("Recieved %d bytes\n", bytes_recieved);
+	printf("\n-=-=-=-=-= Values Recieved (in Network Byte Order) =-=-=-=-=-\n\n");	
+	for(pointerx = (unsigned int *)buffer; counterx < 4; ++counterx, ++pointerx)
+	{
+		printf("[-]Valuex%d : 0x%x\n", counterx+1, *pointerx);
+	}
+
+	printf("\n-=-=-=-=-= Values Converted (in Host Byte Order) =-=-=-=-=-\n\n");	
+	for (pointer = (unsigned int *)buffer; counter < 4; ++counter, ++pointer )
+	{
+		return_value = ntohl( (uint32_t )(*pointer) );
+		sum += return_value;
+		printf("[+]Value%d : 0x%x\n", counter+1, return_value);
+	}
+
+
+	// Converting sum to big endian
+    printf("\nsum is : 0x%lx : %d\n", sum, sizeof sum);
+
+	void *payload = (void *)&sum;	
+
+	printf("final payload : %s\n", payload);
+	send(sockfd, payload, sizeof payload, 0);
+	printf("\n0x%lx -----", *((uint64_t *)payload));
+
+
+	char result[500];
+	recv(sockfd, (void *)result, 500, 0);
+
+
+return 0;
+}
+
+
+

Beej_network_programs/showip.c

@@ -0,0 +1,124 @@
+// Author : Abhinav Thakur
+// Email  : [email protected]
+
+/* 
+
+In /usr/include/netdb.h
+
+struct addrinfo
+{
+  int ai_flags;					// Input flags.  
+  int ai_family;				// Protocol family for socket.  
+  int ai_socktype;				// Socket type.  
+  int ai_protocol;				// Protocol for socket.  
+  socklen_t ai_addrlen;			// Length of socket address. 
+  struct sockaddr *ai_addr;		// Socket address for socket.  
+  char *ai_canonname;			// Canonical name for service location.  
+  struct addrinfo *ai_next;		// Pointer to next in list.  
+};
+
+
+
+In /usr/include/netinet/in.h
+
+// for IPv4
+struct sockaddr_in
+{
+    __SOCKADDR_COMMON (sin_);
+    in_port_t sin_port;				// Port number.  
+    struct in_addr sin_addr;		// Internet address.  
+
+    // Pad to size of `struct sockaddr'.  
+    unsigned char sin_zero[sizeof (struct sockaddr) -
+			   __SOCKADDR_COMMON_SIZE -
+			   sizeof (in_port_t) -
+			   sizeof (struct in_addr)];
+};
+
+// Ditto, for IPv6.  
+struct sockaddr_in6
+{
+    __SOCKADDR_COMMON (sin6_);
+    in_port_t sin6_port;			// Transport layer port #
+    uint32_t sin6_flowinfo;			// IPv6 flow information 
+    struct in6_addr sin6_addr;		// IPv6 address 
+    uint32_t sin6_scope_id;			// IPv6 scope-id 
+};
+
+*/
+
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+
+#define FAMILY AF_UNSPEC
+#define SOCKTYPE SOCK_STREAM
+
+
+int main(int argc, char *argv[])
+{
+	struct addrinfo hints, *server_info;
+	struct addrinfo *ptr = NULL;
+	int status;
+	char ipstr[INET6_ADDRSTRLEN];
+
+
+	// check for the command line args
+	if (argc < 2)
+	{
+		printf("Usage: %s <domain_name>\n", argv[0]);
+		return 0x10;
+	}
+
+	// zero out the structure provided_info initially and fill in the
+	// ai_family and ai_socktype members of provided_info structure.
+	memset( &hints, 0, sizeof hints );	
+	hints.ai_family = FAMILY;			
+	hints.ai_socktype = SOCKTYPE;
+
+	// getaddrinfo() returning the resulting linked list of struct addrinfo to 'server_info'
+	status = getaddrinfo(argv[1], NULL, &hints, &server_info);
+	if (status != 0)
+	{
+		fprintf(stderr, "%s\n", gai_strerror(status));
+		exit(0x11);
+	}
+
+	// parse through linked list and print the IP addresses of
+	// the struct addrinfo linked lists returned
+	for (ptr = server_info; ptr != NULL; ptr = ptr->ai_next)
+	{
+		char *ip_version;
+		void *ip_address;
+
+		// check if the family is IPv4
+		if (ptr->ai_family == AF_INET)
+		{
+			struct sockaddr_in *ipv4 = (struct sockaddr_in *)ptr->ai_addr;
+			ip_address = &(ipv4->sin_addr);
+			ip_version = "IPv4";
+		}
+
+		// the family is IPv6
+		else
+		{
+			struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)ptr->ai_addr;
+			ip_address = &(ipv6->sin6_addr);
+			ip_version = "IPv6";	
+		}
+
+		inet_ntop( ptr->ai_family, ip_address, ipstr, sizeof ipstr);	
+		printf("%s: %s\n", ip_version, ipstr);
+	}
+
+	freeaddrinfo(server_info);	
+
+return 0;
+}