added session5 (unfishied)

session5/.gitignore

@@ -0,0 +1,2 @@
+ping/ping
+sniff/sniff

session5/ping/Makefile

@@ -0,0 +1,11 @@
+TARGETS = ping
+
+CC = gcc
+CFLAGS = -g -lrt
+
+all: $(TARGETS) Makefile
+clean:
+	rm -f $(TARGETS)
+	rm -f *.o *~
+
+.PHONY: all clean

session5/ping/ping.c

@@ -0,0 +1,175 @@
+#define _POSIX_C_SOURCE 199309L
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <error.h>
+#include <string.h>
+#include <unistd.h>
+#include <time.h>
+
+#define __USE_BSD 1
+#include <netinet/in_systm.h>
+#include <netinet/ip_icmp.h>
+
+#include <arpa/inet.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#define ICMP_FILTER 1
+#define ECHO_DATA "Hello World"
+
+int hexdump(void *buf, size_t len)
+{
+	uint16_t *data = (uint16_t *) buf;
+	
+	for (size_t i = 0; i < len; i += 2) {
+		if (i % 16 == 0 && i != 0)
+			printf("\n");
+		
+		printf("%04hx ", ntohs(data[i/2]));
+	}
+	printf("\n");
+}
+
+uint16_t icmp_checksum(void *vdata, size_t length)
+{
+	// Cast the data pointer to one that can be indexed.
+	char *data = (char*)vdata;
+
+	// Initialise the accumulator.
+	uint32_t acc = 0xffff;
+
+	// Handle complete 16-bit blocks.
+	for (size_t i = 0; i + 1 < length; i += 2) {
+		uint16_t word;
+		memcpy(&word, data+i,2);
+		acc += ntohs(word);
+		if (acc > 0xffff)
+			acc -= 0xffff;
+	}
+
+	// Handle any partial block at the end of the data.
+	if (length & 1) {
+		uint16_t word = 0;
+		memcpy(&word, data+length-1, 1);
+		acc += ntohs(word);
+		if (acc > 0xffff)
+			acc -= 0xffff;
+	}
+
+	// Return the checksum in network byte order.
+	return htons(~acc);
+}
+
+int ping(int sd, uint16_t seq, uint16_t id)
+{
+	struct icmp pkg = {
+		.icmp_type = ICMP_ECHO,
+		.icmp_code = 0,
+		.icmp_cksum = 0,
+		.icmp_id = htons(id),
+		.icmp_seq = htons(seq)
+	};
+
+	strcpy(pkg.icmp_data, ECHO_DATA);
+		
+	size_t pkg_len = 8 + strlen(pkg.icmp_data);
+	pkg.icmp_cksum = icmp_checksum(&pkg, pkg_len);
+	
+	ssize_t len = send(sd, &pkg, pkg_len, 0);
+	
+	return len < 0 ? -1 : 0;
+}
+
+int pong(int sd, uint16_t seq, uint16_t id)
+{
+	ssize_t len;
+	char buf[128];
+		
+	len = recv(sd, &buf, sizeof(buf), 0);
+	if (len < 0)
+		return -1;
+	
+	uint8_t ihl = buf[0] & 0xf;
+	uint8_t ttl = buf[8];
+	
+	struct icmp *pkg = (struct icmp *) &buf[ihl * 4];
+	
+	if (!icmp_checksum(&pkg, len))
+		return -2;
+	
+	if (pkg->icmp_type != ICMP_ECHOREPLY ||
+	    pkg->icmp_code != 0)
+		return -3;
+	
+	if (pkg->icmp_id != htons(id) ||
+	    pkg->icmp_seq != htons(seq))
+		return -4;
+	
+	if (strcmp(ECHO_DATA, pkg->icmp_data))
+		return -5;
+	
+	printf("len: %u, ttl: %u, type: %u, code: %u, id: %u, seq: %u, data: %10s", len-ihl*4, ttl,
+		pkg->icmp_type, pkg->icmp_code, ntohs(pkg->icmp_id), ntohs(pkg->icmp_seq), pkg->icmp_data);
+	
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	int ret;
+	struct timespec ts_start, ts_end;
+	struct sockaddr_in sa = {
+		.sin_family = AF_INET
+	};
+	
+	if (argc != 2)
+		error(-1, 0, "Usage: %s IP-ADDRESS", argv[0]);
+	
+	if (inet_pton(AF_INET, argv[1] , &sa.sin_addr) != 1)
+		error(-1, 0, "Failed to parse IP address");
+	
+	int sd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
+	if (sd < 0)
+		error(-1, errno, "Failed to create socket");
+	
+	if (connect(sd, (struct sockaddr*) &sa, sizeof(sa)))
+		error(-1, errno, "Failed to connect socket");
+	
+	/* We only want to receive echo replies */
+	uint32_t data = ~(1 << ICMP_ECHOREPLY);	
+	if (setsockopt(sd, SOL_RAW, ICMP_FILTER, &data, sizeof(data)))
+		error(-1, errno, "Failed socketopt");
+	
+	time_t t;
+	time(&t);
+	srand((unsigned int) t);
+	
+	uint16_t seq = 0;
+	uint16_t id = rand();
+	for (; seq < 10; seq++) {
+		clock_gettime(CLOCK_MONOTONIC, &ts_start);
+		
+		ret = ping(sd, seq, id);
+		if (ret)
+			error(-1, errno, "Failed ping: %d (%s)", ret, strerror(errno));
+		
+		do {
+			ret = pong(sd, seq, id);
+			if (ret)
+				error(0, errno, "Failed pong: %d (%s)", ret, strerror(errno));
+		} while(ret);
+		
+		clock_gettime(CLOCK_MONOTONIC, &ts_end);
+		
+		double rtt = 1e3 * (ts_end.tv_sec - ts_start.tv_sec) + 1e-6 * (ts_end.tv_nsec - ts_start.tv_nsec);
+		printf(", rtt: %f ms\n", rtt);
+		
+		sleep(1);
+	}
+	
+	close(sd);
+	
+	return 0;
+}

session5/sniff/Makefile

@@ -0,0 +1,11 @@
+TARGETS = sniff
+
+CC = gcc
+CFLAGS = -g
+
+all: $(TARGETS) Makefile
+clean:
+	rm -f $(TARGETS)
+	rm -f *.o *~
+
+.PHONY: all clean

session5/sniff/sniff.c

@@ -0,0 +1,111 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <error.h>
+
+#include <sys/socket.h>
+
+#include <linux/if_packet.h>
+#include <net/ethernet.h>
+
+#include <netinet/ether.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <netinet/udp.h>
+#include <netinet/tcp.h>
+
+#define SNAPLEN 1024
+
+const char* icmp_type_str = {
+	[ 0 ] = "Echo Reply",
+	[ 1..2 ] = NULL,	
+	[ 3 ] = "Destination Unreachable",
+	[ 4 ] = "Source Quench",
+	[ 5 ] = "Redirect",
+	[ 6 ] = "Alternate Host Address",
+	[ 7 ] = NULL,
+	[ 8 ] = "Echo",
+	[ 9 ] = "Router Advertisement",
+	[ 10 ] = "Router Solicitation",
+	[ 11 ] = "Time Exceeded",
+	[ 12 ] = "Parameter Problem",
+	[ 13 ] = "Timestamp",
+	[ 14 ] = "Timestamp Reply",
+	[ 15 ] = "Information Request",
+	[ 16 ] = "Information Reply",
+	[ 17 ] = "Address Mask Request",
+	[ 18 ] = "Address Mask Reply"
+}
+
+int hexdump(void *buf, size_t len)
+{
+	uint16_t *data = (uint16_t *) buf;
+	
+	for (size_t i = 0; i < len; i += 2) {
+		if (i % 16 == 0 && i != 0)
+			printf("\n");
+		
+		printf("%04hx ", ntohs(data[i/2]));
+	}
+	printf("\n");
+}
+
+int parse_packet(uint8_t *data, size_t len)
+{
+	/* Parse Ethertype */
+	struct ether_header *ehdr = data;
+	
+	printf("ether_src: %s ", ether_ntoa(ehdr->ether_shost));
+	printf("ether_dst: %s ", ether_ntoa(ehdr->ether_dhost));
+	printf("ether_type: %#04x ", ehdr->ether_type);
+	
+	if (ehdr->ether_type == ETHERTYPE_IP) {
+		/* Parse IP protocol */
+		struct ip *iphdr = (char *) ehdr + sizeof(*ehdr)
+		
+		printf("ip_version: %u ", iphdr->ip_v);
+		printf("ip_ihl: %u ", iphdr->ip_hl);
+		printf("ip_ttl: %u ", iphdr->ip_ttl);
+		printf("ip_protocol: %u ", iphdr->ip_p);
+		printf("ip_src: %u ", iphdr->ip_p);
+		printf("ip_dst: %u ", iphdr->ip_p);
+	
+		if (iphdr->p == IPPROTO_ICMP) {
+			/* Parse ICMP */
+			struct icmphdr *icmphdr = (char *) iphdr + iphdr->ip_hl * 4;
+			
+			printf("icmp_type: %u (%s) ");
+			printf("icmp_code: %u ")
+		}
+		else if (iphdr->p == IPPROTO_UDP) {
+			/* Parse UDP */
+			struct udphdr *udphdr = (char *) udphdr + iphdr->ip_hl * 4;
+	
+		}
+		else if (iphdr->p == IPPROTO_TCP) {
+			/* Parse TCP */
+			struct udphdr *udphdr = (char *) udphdr + iphdr->ip_hl * 4;
+			
+		}
+	}
+}
+
+int main (int argc, char *argv[])
+{
+	uint8_t packet[SNAPLEN];
+
+	int sd = socket(AF_INET, SOCK_RAW, htons(ETH_P_ALL));
+	if (sd < 0)
+		error(-1, errno, "Failed to create socket");
+	
+	
+	while (1) {
+		if (recv(sd, packet, sizeof(packet), 0) > 0)
+			parse_packet(packet, sizeof(packet));
+	}
+	
+	close(sd);
+	
+	return 0;
+}