From 999ce761bae19a3827acc2bdd39aefb783c5e399 Mon Sep 17 00:00:00 2001
From: hippoz <10706925-hippoz@users.noreply.gitlab.com>
Date: Wed, 14 Sep 2022 10:07:25 +0300
Subject: [PATCH] initial commit

---
 Makefile |   2 +
 main.c   | 171 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 173 insertions(+)
 create mode 100644 Makefile
 create mode 100644 main.c

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..516e7c3
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,2 @@
+main: main.c
+	cc -o main main.c
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..79b26d2
--- /dev/null
+++ b/main.c
@@ -0,0 +1,171 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <poll.h>
+#include <unistd.h>
+
+#define MAX_CLIENTS 512
+#define BACKLOG 10
+#define DIE(info) ({perror((info)); exit(EXIT_FAILURE);})
+
+static const char *socket_path = "/tmp/plumb-unix0";
+
+struct plumb_client {
+    int fd;
+};
+
+struct plumb_server {
+    int socket_fd;
+    int fd_num;
+    struct plumb_client clients[MAX_CLIENTS];
+    struct pollfd fds[MAX_CLIENTS + 1];
+};
+
+
+int plumb_server_client_add(struct plumb_server *s, int fd)
+{
+    printf("adding new connection, fd=%d\n", fd);
+
+    for (int i = 0; i < MAX_CLIENTS; i++) {
+        if (s->clients[i].fd < 0) {
+            s->clients[i].fd = fd;
+            s->fds[i].fd = fd;
+            s->fds[i].events = POLLIN;
+            return i;
+        }
+    }
+    return -1;
+}
+
+void plumb_server_client_remove(struct plumb_server *s, int i)
+{
+    if (i >= MAX_CLIENTS)
+        return;
+
+    printf("removing client i=%d\n", i);
+
+    if (s->clients[i].fd >= 0) {
+        close(s->clients[i].fd);
+    }
+    s->clients[i].fd = -1;
+    s->fds[i].fd = -1;
+    s->fds[i].events = 0;
+    s->fds[i].revents = 0;
+}
+
+
+void plumb_server_free(struct plumb_server *s)
+{
+    if (!s) return;
+    if (s->socket_fd) close(s->socket_fd);
+    free(s);
+}
+
+struct plumb_server *plumb_server_create()
+{
+    struct plumb_server *s = malloc(sizeof(struct plumb_server));
+    if (s == NULL) {
+        DIE("malloc");
+        return NULL;
+    }
+
+    s->socket_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (s->socket_fd == -1) {
+        free(s);
+        DIE("socket");
+        return NULL;
+    }
+
+    struct sockaddr_un name;
+    memset(&name, 0, sizeof(name));
+    name.sun_family = AF_UNIX;
+    strncpy(name.sun_path, socket_path, sizeof(name.sun_path) - 1);
+
+    if (bind(s->socket_fd, (const struct sockaddr *)&name, sizeof(name)) == -1) {
+        free(s);
+        close(s->socket_fd);
+        DIE("bind");
+        return NULL;
+    }
+    if (listen(s->socket_fd, BACKLOG) == -1) {
+        free(s);
+        close(s->socket_fd);
+        DIE("listen");
+        return NULL;
+    }
+
+    for (int i = 0; i < MAX_CLIENTS; i++) {
+        s->clients[i].fd = -1;
+        s->fds[i].fd = -1;
+        s->fds[i].events = 0;
+        s->fds[i].revents = 0;
+    }
+
+    s->fds[MAX_CLIENTS].fd = s->socket_fd;
+    s->fds[MAX_CLIENTS].events = POLLIN;
+
+    s->fd_num = MAX_CLIENTS + 1;
+
+    return s;
+}
+
+int plumb_server_turn(struct plumb_server *s)
+{
+    if (poll(s->fds, s->fd_num, -1) < 0) {
+        DIE("poll");
+        return -1;
+    }
+
+    for (int i = 0; i < s->fd_num; i++) {
+        if (s->fds[i].revents & POLLIN) { // file descriptor ready for reading
+            if (s->fds[i].fd == s->socket_fd) { // new connection
+                int fd = accept(s->socket_fd, NULL, NULL);
+                if (fd == -1) {
+                    DIE("accept");
+                    return -1;
+                }
+
+                if (plumb_server_client_add(s, fd) == -1) {
+                    close(fd);
+                    continue;
+                }
+            } else { // data from socket
+                char data[256];
+                memset(data, 0, sizeof(data));
+                ssize_t bytes = recv(s->fds[i].fd, data, sizeof(data), 0);
+                if (bytes == -1) {
+                    DIE("recv");
+                    return -1;
+                } else if (bytes == 0) { // client disconnected
+                    plumb_server_client_remove(s, i);
+                } else {
+                    send(s->fds[i].fd, data, sizeof(data), 0);
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+
+int main()
+{
+    struct plumb_server *srv = plumb_server_create();
+    if (srv == NULL) {
+        fprintf(stderr, "plumb_server_create failed\n");
+        return EXIT_FAILURE;
+    }
+
+    while (1) {
+        if (plumb_server_turn(srv) < 0) {
+            fprintf(stderr, "plumb_server_turn failed\n");
+            plumb_server_free(srv);
+            return EXIT_FAILURE;
+        }
+    }
+
+    plumb_server_free(srv);
+
+    return EXIT_SUCCESS;
+}