From e6c94b64a05cd749e569d52f08f44ff307f2097c Mon Sep 17 00:00:00 2001
From: "Alexander \"Arav\" Andreev" <me@arav.su>
Date: Fri, 22 Mar 2024 03:50:58 +0400
Subject: [PATCH] First try to implement a network module.

---
 src/net.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/net.h | 24 +++++++++++++++++
 2 files changed, 105 insertions(+)
 create mode 100644 src/net.c
 create mode 100644 src/net.h

diff --git a/src/net.c b/src/net.c
new file mode 100644
index 0000000..70caa0b
--- /dev/null
+++ b/src/net.c
@@ -0,0 +1,81 @@
+#include "net.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <arpa/inet.h>
+
+int net_client_init(net_t *const n, const int af_family, const char *const raddr, const int rport) {
+    if ((n->fd = socket(af_family, SOCK_DGRAM, 0)) == -1 )
+        return -1;
+
+    memset(&n->inaddr, 0, sizeof(n->inaddr));
+    n->inaddr_len = sizeof(n->inaddr);
+
+    memset(&n->raddr, 0, sizeof(n->raddr));
+    n->raddr.sin_family = af_family;
+    n->raddr.sin_addr.s_addr = inet_addr(raddr);
+    n->raddr.sin_port = htons(rport);
+
+    return 0;
+}
+
+int net_server_init(net_t *const n, const int af_family, const char *const laddr, const int lport) {
+    if ((n->fd = socket(af_family, SOCK_DGRAM, 0)) == -1 )
+        return -1;
+
+    memset(&n->inaddr, 0, sizeof(n->inaddr));
+    n->inaddr_len = sizeof(n->inaddr);
+
+    memset(&n->laddr, 0, sizeof(n->laddr));
+    n->laddr.sin_family = af_family;
+    n->laddr.sin_addr.s_addr = inet_addr(laddr);
+    n->laddr.sin_port = htons(lport);
+
+    memset(&n->raddr, 0, sizeof(n->raddr));
+    n->raddr_len = sizeof(n->raddr);
+
+    if (bind(n->fd, (struct sockaddr *)&n->laddr, sizeof(n->laddr)) == -1)
+        return -1;
+
+    return 0;
+}
+
+void net_destroy(net_t *n) {
+    if (n->fd > 0) {
+        close(n->fd);
+        n->fd = -1;
+    }
+
+    memset(&n->raddr, 0, sizeof(n->raddr));
+    n->raddr_len = sizeof(n->raddr);
+    memset(&n->laddr, 0, sizeof(n->laddr));
+
+    memset(&n->buffer, 0, NET_BUFLEN);
+}
+
+int net_sendto(net_t *const n, const char *const buf, const int buf_len) {
+    if (n->fd == -1)
+        return -1;
+
+    if (sendto(n->fd, buf, buf_len, 0, (struct sockaddr *)&n->raddr, sizeof(n->raddr)) == -1)
+        return -1;
+
+    return 0;
+}
+
+int net_recvfrom(net_t *const n) {
+    if (n->fd == -1 || n->raddr.sin_addr.s_addr == 0)
+        return -1;
+
+    if ((recvfrom(n->fd, n->buffer, NET_BUFLEN, 0, (struct sockaddr *)&n->inaddr, &n->inaddr_len)) == -1)
+        return -1;
+
+    if (n->raddr.sin_addr.s_addr != n->inaddr.sin_addr.s_addr) {
+        /* Incoming packet doesn't originate from the one we are talking to. Drop it. */
+        return 0;
+    }
+
+    return 0;
+}
diff --git a/src/net.h b/src/net.h
new file mode 100644
index 0000000..c15b8c1
--- /dev/null
+++ b/src/net.h
@@ -0,0 +1,24 @@
+#ifndef _NET_H_
+#define _NET_H_
+
+#include <sys/socket.h>
+#include <netinet/in.h>
+
+#define NET_BUFLEN 256
+
+typedef struct net_t {
+    int fd;
+    struct sockaddr_in laddr, raddr, inaddr;
+    socklen_t raddr_len, inaddr_len;
+
+    char buffer[NET_BUFLEN];
+} net_t;
+
+int net_client_init(net_t *const n, const int af_family, const char *const raddr, const int rport);
+int net_server_init(net_t *const n, const int af_family, const char *const laddr, const int lport);
+void net_destroy(net_t *n);
+
+int net_sendto(net_t *const n, const char *const buf, const int buf_len);
+int net_recvfrom(net_t *const n);
+
+#endif /* _NET_H_ */
\ No newline at end of file