RTM Project

app/shm_ip.c

@@ -0,0 +1,101 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/shm.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <errno.h>
+
+#include "routing-table.h"
+
+/*
+* Stores IP address in newly created shared memory region
+* corresponding to its key, which is a MAC address. Returns
+* the size of created shm on success otherwise -1 on failure.
+*/
+
+int store_IP(const char* mac, const char* ip) {
+
+	size_t size = strlen(ip); // account for terminating null byte
+
+	int shm_fd = shm_open(mac, O_CREAT | O_RDWR | O_TRUNC, 0660);
+
+	if (shm_fd == -1) {
+		printf("Could not create shared memory for MAC %s - IP %s pair\n",
+			mac,
+			ip);
+		return -1;
+	}
+
+	if (ftruncate(shm_fd, size) == -1) {
+		printf("Error on ftruncate to allocate size for IP %s\n", ip);
+		return -1;
+	}
+
+	void* shm_reg = mmap(NULL,
+		size,
+		PROT_READ | PROT_WRITE,
+		MAP_SHARED,
+		shm_fd,
+		0);
+
+	if (shm_reg == MAP_FAILED) {
+		printf("Mapping failed\n");
+		return -1;
+	}
+
+	memset(shm_reg, 0, size);
+	memcpy(shm_reg, ip, size);
+
+	if (munmap(shm_reg, size) == -1) {
+		printf("Unmapping failed\n");
+		return -1;
+	}
+
+	close(shm_fd);
+	return size;
+}
+
+/*
+* Get the IP address corresponding to the MAC address
+* from the shared region that the server created.
+* Returns number of bytes on success else -1 on
+* failure.
+*/
+
+int get_IP(const char* mac, char* ip) {
+
+	int shm_fd = shm_open(mac,
+		O_CREAT | O_RDONLY,
+		0660);
+
+	if (shm_fd == -1) {
+		printf("Couldn't open shared memory for MAC %s - IP %s pair\n",
+			mac,
+			ip);
+		return -1;
+	}
+
+	void* shm_reg = mmap(NULL,
+		IP_ADDR_LEN,
+		PROT_READ,
+		MAP_SHARED,
+		shm_fd,
+		0);
+
+	if (shm_reg == MAP_FAILED) {
+		printf("Mapping failed\n");
+		return -1;
+	}
+
+	memcpy(ip, shm_reg, IP_ADDR_LEN);
+	if (munmap(shm_reg, IP_ADDR_LEN) == -1) {
+		printf("Unmapping failed\n");
+		return -1;
+	}
+
+	close(shm_fd);
+	return strlen(ip);
+}