initial commit

src/Makefile

@@ -0,0 +1,10 @@
+CC=gcc
+CFLAGS=-g -I.
+DEPS=
+OBJ=main.o
+
+%.o: %.c $(DEPS)
+	$(CC) -c -o $@ $< $(CFLAGS)
+
+csyslog: $(OBJ)
+	gcc -o $@ $^ $(CFLAGS)

src/main.c

@@ -0,0 +1,132 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <ctype.h>
+#include <string.h>
+#include <assert.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <limits.h>
+
+// Mostly lifted from https://cs.nyu.edu/~mwalfish/classes/16sp/classnotes/handout01.pdf
+
+void panic(const char* s) {
+    perror(s);
+    exit(1);
+}
+
+struct Message {
+    int priority;
+};
+
+int parse_message(struct Message* result, char* message) {
+    /*
+        parse a message like:
+            <134>May 10 03:09:59 filterlog: 5,,,1000000103,cpsw0,match,block,in,4,0x20,,239,27547,0,none,6,tcp,40,185.216.140.37,24.4.129.164,57159,11111,0,S,3919167832,,1024,,
+        Format:
+            <priority>VERSION ISOTIMESTAMP HOSTNAME APPLICATION PID MESSAGEID STRUCTURED-DATA MSG
+        Assumes null termed string
+    */
+    printf("Got message: %s\n", message);
+
+    // Must have >3 chars to form <x> priority
+    if (strlen(message) < 3) return 1;
+    // Must start with <
+    if (message[0] != '<') return 1;
+
+    printf("%lu\n", strlen(message));
+    // const char delim = " "
+
+    char digits[] = "\0\0\0";
+    int num_digits = 0;
+    int position = 1;
+    //bool found_priority_end = false; // TODO
+
+    while (position < 4) {
+        printf("inspecting %c\n", message[position]);
+        if(!isdigit(message[position])) return 1; // priority must be numeric
+        digits[num_digits] = message[position];
+        num_digits++;
+        position++;
+        if (message[position] == '>') {
+            break;
+        }
+        // break;
+    }
+    if (num_digits == 0) return 1; // empty priority >< ?
+
+    printf("found digits %d, aka %d\n", atoi(digits), atoi(digits)/2);
+    // result = Message{atoi(digits)};
+    result->priority = atoi(digits);
+
+    // assert(0);
+    // *strtok(char *str, const char *delim)
+}
+
+int main(int argc, char** argv) {
+    int sock_fd;
+    struct sockaddr_in my_addr, my_peer_addr;
+    char* endptr;
+    unsigned int portl;
+    unsigned short port;
+    int size_recvd;
+    char msg[1024];
+    socklen_t addrlen;
+
+    if (argc != 2) {
+        fprintf(stderr, "usage: %s <port>\n", argv[0]);
+        exit(1);
+    }
+
+    /* convert from string to int */
+    portl = strtol(argv[1], &endptr, 10);
+    if (endptr == NULL || portl == 0)
+    panic("strtol");
+
+    assert(portl < USHRT_MAX);
+    port = (unsigned short)portl;
+
+    /*
+    * Note! This code is not the same as what you need to do in lab1.
+    */
+    if ((sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
+        panic("socket");
+    int one = 1;
+    setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(1));
+
+    memset(&my_addr, 0, sizeof(my_addr));
+    my_addr.sin_family = AF_INET;
+    my_addr.sin_addr.s_addr = INADDR_ANY;
+    my_addr.sin_port = htons(port);
+
+    if (bind(sock_fd, (struct sockaddr*)&my_addr, sizeof(struct sockaddr_in)) < 0)
+        panic("bind failed");
+
+    while (1) {
+        addrlen = sizeof(struct sockaddr_in);
+
+        if ((size_recvd = recvfrom(sock_fd, /* socket */
+                                     msg, /* buffer */
+                                     sizeof(msg), /* size of buffer */
+                                     0, /* flags = 0 */
+                                     (struct sockaddr*)&my_peer_addr, /* who’s sending */
+                                     &addrlen /* length of buffer to receive peer info */
+                                    )) < 0)
+            panic("recvfrom");
+
+        assert(addrlen == sizeof(struct sockaddr_in));
+
+        // TODO should we check that msg[size_recvd] == \0 ?
+        // printf("From host %s src port %d got message %.*s\n",
+        //        inet_ntoa(my_peer_addr.sin_addr), ntohs(my_peer_addr.sin_port), size_recvd, msg);
+        struct Message result;
+        // printf("XXXsize: %lu", sizeof(result)); // curious how big the struct gets
+        if(parse_message(&result, msg)) {
+            printf("message is valid, priority %d\n", result.priority);
+        }
+    }
+
+    exit(EXIT_SUCCESS);
+}