From 9526d60b2cf092444af86924288c222d804a36a3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Anton=20Luka=20=C5=A0ijanec?= <anton@sijanec.eu>
Date: Wed, 12 Jan 2022 22:14:32 +0100
Subject: =?UTF-8?q?pcap=20in=20host=C5=A1t+net->hostip?=
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---
 host.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 host.c

(limited to 'host.c')

diff --git a/host.c b/host.c
new file mode 100644
index 0000000..b6e68dd
--- /dev/null
+++ b/host.c
@@ -0,0 +1,95 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <sys/types.h>
+#include <netdb.h>
+struct in_net {
+	struct in_addr addr;
+	struct in_addr mask;
+};
+/* not needed begin */
+#define POPCNT(y) int popcnt##x (uint##y##_t x) { \
+	int c = 0; \
+	for (int i = 0; i < y; i++) \
+		if (1 << i & x) \
+			c++; \
+	return c; \
+}
+POPCNT(32)
+unsigned int power2[] = { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456, 536870912, 1073741824, 2147483648 }; /* ah yes, libmath */
+/* not needed end */
+struct in_addr host (struct in_net n, int h /* consecutive number of the host in the network */) {
+	n.addr.s_addr = ntohl(n.addr.s_addr & n.mask.s_addr);
+	n.mask.s_addr = ntohl(n.mask.s_addr);
+	int c = 1;
+	int s = 0;
+	for (int i = 0; i < 32; i++)
+		if (1 << i & ~n.mask.s_addr) {
+			if (1 << s++ & h)
+				n.addr.s_addr |= 1 << i;
+			c = c * 2;
+		}
+	if (h >= c)
+		n.addr.s_addr = 0;
+	n.addr.s_addr = htonl(n.addr.s_addr);
+	return n.addr;
+}
+int resolve (const char * d, uint32_t * r) {
+	struct addrinfo hints = {
+		.ai_family = AF_INET,
+		.ai_socktype = SOCK_DGRAM,
+		.ai_flags = 0,
+		.ai_protocol = 0,
+		.ai_canonname = NULL,
+		.ai_addr = NULL,
+		.ai_next = NULL
+	};
+	struct addrinfo * result;
+	int ret = getaddrinfo(d, NULL, &hints, &result);
+	*r = ((struct sockaddr_in *) result->ai_addr)->sin_addr.s_addr; /* ah yes, C */
+	freeaddrinfo(result);
+	return ret;
+}
+struct in_net str2net (char * s) { /* blocking, resolving */
+	struct in_net r = {
+		.mask = {
+			.s_addr = 0
+		},
+		.addr = {
+			.s_addr = 0
+		}
+	};
+	char * m = strchr(s, '/');
+	char o = '\0';
+	int e;
+	if (m) {
+		o = *m;
+		*m++ = '\0';
+	} else
+		m = "32";
+	fprintf(stderr, "str2net: resolving %s ... ", s);
+	if ((e = resolve(s, &r.addr.s_addr))) {
+		fprintf(stderr, "failed: %s\n", gai_strerror(e));
+		goto r;
+	}
+	fprintf(stderr, " %s mask %s ...", inet_ntoa(r.addr), m);
+	char * p;
+	int x = strtoll(m, &p, 10);
+	r.mask.s_addr = 0;
+	for (int j = 0; j < x && j < 32; j++)
+		r.mask.s_addr = r.mask.s_addr >> 1 | 1 << 31;
+	r.mask.s_addr = htonl(r.mask.s_addr);
+	if (*p)
+		if ((e = resolve(m, &r.mask.s_addr))) {
+			fprintf(stderr, "no: %s\n", gai_strerror(e));
+			goto r;
+		}
+	fprintf(stderr, " %s\n", inet_ntoa(r.mask));
+r:
+	if (o)
+		*--m = o;
+	return r;
+}
-- 
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