Implement Server (#1)

- Generic Server struct
- TCP and UDP

Reviewed-on: #1

src/input.c

@@ -2,6 +2,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
+#include <errno.h>
 
 #ifdef __linux__
 
@@ -121,3 +122,18 @@ void del_split(char **sp) {
 void del_lines(char **lines) {
     del_split(lines);
 }
+
+const char *capture_system(const char *cmd, int buf_sz) {
+    if (buf_sz == 0) {
+        buf_sz = DEFAULT_CAPTURE_SYSTEM_BUFSIZE;
+    }
+    char *buf = malloc(buf_sz);
+    FILE *tmp = popen(cmd, "r");
+    if (tmp == NULL) {
+        fprintf(stderr, "libflint: failed to open FILE *tmp in capture_system. Errno: %d\n", errno);
+        free(buf);
+        return NULL;
+    }
+    fgets(buf, buf_sz, tmp);
+    return buf;
+}

src/network.c

@@ -0,0 +1,150 @@
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <arpa/inet.h>
+#include <sys/wait.h>
+#include <netdb.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <signal.h>
+#include <pthread.h>
+
+#include "lfnetwork.h"
+
+static void sighandler(int s) {
+    int saved_errno = errno;
+    while (waitpid(-1, NULL, WNOHANG) > 0);
+    errno = saved_errno;
+}
+
+void *get_in_addr(struct sockaddr *sa)
+{
+    if (sa->sa_family == AF_INET) {
+        return &(((struct sockaddr_in*)sa)->sin_addr);
+    }
+
+    return &(((struct sockaddr_in6*)sa)->sin6_addr);
+}
+
+Server *new_server(ServerType type, const char *port, void(handler)(Server *s)) {
+    Server *s = (Server *)malloc(sizeof(Server));
+    if (s == NULL) {
+        return NULL;
+    }
+    s->server_type = type;
+    s->handler = handler;
+
+    struct addrinfo *addr = NULL;
+    if (getaddrinfo(NULL, port, NULL, &addr) != 0) {
+        free(s);
+        return NULL;
+    }
+    s->port = (int)strtol(port, NULL, 10);
+
+    int socktype = 0;
+    switch (type) {
+    case SERVERTYPE_TCP:
+        socktype = SOCK_STREAM;
+        break;
+    case SERVERTYPE_UDP:
+        socktype = SOCK_DGRAM;
+        break;
+    }
+
+    struct addrinfo *p;
+    for (p = addr; p != NULL; p = p->ai_next) {
+        s->fd = socket(AF_INET, socktype, 0);
+        if (s->fd == -1) {
+            continue;
+        }
+
+        if (bind(s->fd, p->ai_addr, p->ai_addrlen) != 0) {
+            close(s->fd);
+            continue;
+        }
+
+        break;
+    }
+
+    if (p == NULL) {
+        fprintf(stderr, "Failed to bind\n");
+        free(s);
+        return NULL;
+    }
+
+    freeaddrinfo(addr);
+    return s;
+}
+
+void delete_server(Server *s) {
+    free(s);
+    s = NULL;
+}
+
+int serve(Server *s, int backlog_size) {
+    if (backlog_size == 0) {
+        backlog_size = DEFAULT_BACKLOG;
+    }
+
+    if (listen(s->fd, backlog_size) != 0) {
+        return 1;
+    }
+
+    // Linux doesn't handle SA_RESTART properly, and I don't know about Windows (nor do I care)
+    // This is just for macOS and BSDs
+    #if !defined(__linux__) && !defined(_WIN32)
+    struct sigaction sa;
+    sa.sa_handler = sighandler; 
+    sa.sa_flags = SA_RESTART;
+    if (sigaction(SIGCHLD, &sa, NULL) == -1) {
+        fprintf(stderr, "Failed to set sigaction\n");
+        return 1;
+    }
+    #endif
+
+    s->handler(s);
+
+    return 0;
+}
+
+static void *tcp_echo_thread(void *vargp) {
+    while (1) {
+        char recv_buf[256];
+        int fd = *(int *) vargp;
+
+        int r = (int)recv(fd, recv_buf, 256, 0);
+        if (r < 1) {
+            if (r == -1) {
+                fprintf(stderr, "Failed to recv. Errno: %d\n", errno);
+            }
+            close(fd);
+            break;
+        }
+
+        if (send(fd, recv_buf, strlen(recv_buf), 0) == -1) {
+            fprintf(stderr, "Failed to send echo. Errno: %d\n", errno);
+            close(fd);
+            break;
+        }
+    }
+}
+
+void handler_tcp_echo(Server *s) {
+    while (1) {
+        struct sockaddr_storage client_addr;
+        socklen_t client_addr_sz = sizeof(client_addr);
+        int new_fd = accept(s->fd, (struct sockaddr *)&client_addr, &client_addr_sz);
+        if (new_fd == -1) {
+            fprintf(stderr, "failed to accept. Errno: %d\n", errno);
+            continue;
+        }
+
+        pthread_t srv_tid;
+        pthread_attr_t attr;
+        pthread_attr_init(&attr);
+        pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+        pthread_create(&srv_tid, &attr, tcp_echo_thread, &new_fd);
+    }
+}