From 2278df1493e064c197913e49b5d1935942d83448 Mon Sep 17 00:00:00 2001
From: daniel <daniel@planethacker.net>
Date: Tue, 6 May 2025 16:57:32 -0700
Subject: initial import

---
 src/net.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 src/net.c

(limited to 'src/net.c')

diff --git a/src/net.c b/src/net.c
new file mode 100644
index 0000000..02c3d6e
--- /dev/null
+++ b/src/net.c
@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include <net/if.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+
+
+int sockprintf(int s, const char *fmt, ...) {
+	int     n;
+	char    buf[8192] = {0};
+	va_list vl;
+
+	va_start(vl, fmt);
+	n = vsnprintf(buf, sizeof(buf), fmt, vl);
+	va_end(vl);
+
+	return send(s, buf, n, 0);
+}
+
+bool validate_ipv4(const char *ip) {
+	return inet_aton(ip, NULL) ? true : false;
+}
+
+bool validate_ip(const char *ip) {
+	struct in_addr  addr4;
+	struct in6_addr addr6;
+
+	return inet_pton(AF_INET, ip, &addr4) == 1 || inet_pton(AF_INET6, ip, &addr6) == 1;
+}
+
+// get the interface assigned to the default route. this is a sensible
+// default for most deployments, but not perfect.
+char *get_default_iface(void) {
+	static char iface[IFNAMSIZ] = {0};
+	FILE *fp = fopen("/proc/net/route", "r");
+	if (!fp) {
+		return NULL;
+	}
+
+	char line[256];
+	fgets(line, sizeof(line), fp); // skip header line
+	while (fgets(line, sizeof(line), fp)) {
+		char iface_name[IFNAMSIZ];
+		unsigned long dest;
+		if (sscanf(line, "%s %lx", iface_name, &dest) == 2) {
+			if (dest == 0) { // default route
+				strncpy(iface, iface_name, IFNAMSIZ - 1);
+				fclose(fp);
+				return iface;
+			}
+		}
+	}
+
+	fclose(fp);
+	return NULL;
+}
-- 
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