init

.gitignore

@@ -0,0 +1,2 @@
+build
+obj

Makefile

@@ -0,0 +1,33 @@
+NAME := ft_ping
+
+CC := gcc
+CFLAGS := -Wall -Wextra -Werror -g
+
+LD := $(CC)
+LDFLAGS := 
+
+SRC := $(shell find src -name '*.c')
+OBJ := $(patsubst src/%.c,obj/%.o,$(SRC))
+
+all: $(NAME)
+
+obj/%.o: src/%.c
+	mkdir -p $(dir $@)
+	$(CC) $(CFLAGS) -c $< -o $@
+
+$(NAME): $(OBJ)
+	mkdir -p build
+	$(LD) $(LDFLAGS) -o build/$(NAME) $(OBJ) 
+
+clean:
+	rm -rf obj
+
+fclean: clean
+	rm -rf build
+
+re: 
+	$(MAKE) fclean 
+	$(MAKE) all
+
+.PHONY: all clean fclean re
+-include $(DEP)

src/main.c

@@ -0,0 +1,204 @@
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <stdarg.h>
+#include <netinet/ip_icmp.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <time.h>
+
+void print_err(const char *format, ...)
+{
+    va_list args;
+
+    puts("ft_ping: ");
+    va_start(args, format);
+    vprintf(format, args);
+    va_end(args);
+    putchar('\n');
+}
+
+unsigned short checksum(void *b, int len) {
+    unsigned short *buf = b;
+    unsigned int sum = 0;
+    unsigned short result;
+
+    for (sum = 0; len > 1; len -= 2)
+        sum += *buf++;
+    if (len == 1)
+        sum += *(unsigned char *)buf;
+    sum = (sum >> 16) + (sum & 0xFFFF);
+    sum += (sum >> 16);
+    result = ~sum;
+    return result;
+}
+
+int pktcmp(const char *sent, const char *received, size_t packet_size)
+{
+    const struct icmphdr *sent_hdr = (const struct icmphdr*) sent;
+    const struct icmphdr *received_hdr = (const struct icmphdr*) received;
+    
+    if (received_hdr->type != 0 || received_hdr->code != 8)
+        return 1;
+
+    if (received_hdr->un.echo.sequence == sent_hdr->un.echo.sequence)
+        return 2;
+
+    const char *sent_payload = sent + sizeof(struct icmphdr);
+    const char *received_payload = received + sizeof(struct icmphdr);
+
+    return memcmp(sent_payload, received_payload, packet_size - sizeof(struct icmphdr));
+}
+
+int fill_with_random(char *str, size_t nb)
+{
+    int fd;
+    
+    fd = open("/dev/random", O_RDONLY);
+    if (fd < 0)
+    {
+        print_err("error: open /dev/random failed.");
+        return 1;
+    }
+    if (read(fd, str, nb) != (ssize_t) nb)
+    {
+        close(fd);
+        print_err("error: read /dev/random failed.");
+        return 2;
+    }
+    close(fd);
+    return 0;
+}
+
+int update_packet(char *packet, size_t payload_size)
+{
+    static size_t sequence = 1;
+    size_t hdr_size = sizeof(struct icmphdr);
+    size_t packet_size = hdr_size + payload_size;
+
+    struct icmphdr *hdr = (void*)packet;
+
+    hdr->un.echo.sequence = htons(sequence++);
+    hdr->checksum = 0;
+
+    if (fill_with_random(packet + hdr_size, payload_size))
+    {
+        free(packet);
+        return 1;
+    }
+
+    hdr->checksum = checksum(packet, packet_size);
+    return 0;
+}
+
+void *create_packet(size_t payload_size)
+{
+    size_t hdr_size = sizeof(struct icmphdr);
+    size_t packet_size = hdr_size + payload_size;
+
+    char *packet;
+
+    packet = malloc(packet_size);
+    if (packet == NULL)
+    {
+        print_err("allocation failed.");
+        return NULL;
+    }
+
+    struct icmphdr *hdr = (struct icmphdr *)packet;
+
+    hdr->type = ICMP_ECHO;
+    hdr->code = 0;
+    hdr->un.echo.id = htons(getpid() & 0xFFFF);
+
+    update_packet(packet, payload_size);
+
+    return packet;
+}
+
+int packet_check(char *packet, size_t packet_size)
+{
+    struct icmphdr *hdr = (struct icmphdr *) packet;
+    
+    const uint16_t checksum_bak = hdr->checksum;
+    hdr->checksum = 0;
+    int tmp = checksum(packet, packet_size);
+    hdr->checksum = checksum_bak;
+
+    return tmp - checksum_bak;
+}
+
+int main(int ac, char **av)
+{
+    (void) ac;
+    (void) av;
+    size_t payload_size = 48;
+    size_t packet_size = sizeof(struct icmphdr) + payload_size;
+
+    int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
+
+    if (sockfd == -1)
+    {
+        print_err("open socket failed, maybe try in root (:");
+        return 1;
+    }
+
+    struct sockaddr_in dest;
+
+    dest.sin_family = AF_INET;
+    dest.sin_port = htons(0);       
+    inet_pton(AF_INET, "8.8.8.8", &dest.sin_addr);
+
+    while (1) {
+
+        char *packet = create_packet(payload_size);
+        if (packet == NULL)
+        {
+            close(sockfd);
+            return 2;
+        }
+
+        if (sendto(sockfd, packet, packet_size, 0,  (struct sockaddr *) &dest, sizeof(dest)) == -1)
+        {
+            print_err("error: send packet failed.");
+            free(packet);
+            close(sockfd);
+            return 2;
+        }
+        printf("icmp request sent\n");
+
+        char *buffer;
+        buffer = malloc(packet_size * sizeof(char));
+        if (buffer == NULL)
+        {
+            print_err("error: allocation failed.");
+            free(packet);
+            close(sockfd);
+            return 10;
+        }
+        struct sockaddr_in sender;
+        socklen_t len = sizeof(sender); 
+
+        do
+        {
+            if (recvfrom(sockfd, buffer, packet_size, 0, (struct sockaddr *) &sender, &len) < 0)
+            {
+                print_err("error: receive packet failed.");
+                close(sockfd);
+                free(buffer);
+                free(packet);
+                return 3;
+            }
+        }
+        while (len == packet_size && packet_check(buffer, packet_size) == 0 && pktcmp(packet, buffer, packet_size) == 0);
+        free(packet);
+        printf("icmp reply received\n");
+        sleep(1);
+    }
+}