From 95dada12eb1c7c6d52a52b89e4bf1a56b95d692a Mon Sep 17 00:00:00 2001
From: Joel Grunbaum <joelgrun@gmail.com>
Date: Wed, 01 Jun 2022 04:52:13 +0000
Subject: [PATCH] checks for server conductibility if user is root
---
dns.c | 41 +++++++++++++----------------------------
1 files changed, 13 insertions(+), 28 deletions(-)
diff --git a/dns.c b/dns.c
index 9095878..c2053dd 100644
--- a/dns.c
+++ b/dns.c
@@ -7,6 +7,7 @@
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
+#include <netinet/udp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@@ -70,10 +71,6 @@
char* rdata;
};
-#define IP_ICMP 1
-#define IP_TCP 6
-#define IP_UDP 17
-
// Test if an IP address is hosting a DNS server
int reachable(unsigned char* buf, char* dns_ip)
{
@@ -92,10 +89,9 @@
dest.sin_addr.s_addr = inet_addr(dns_ip);
s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
- /* r = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP); */
r = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL));
if (r < 0) {
- printf("%d, %s\n", r, strerror(errno));
+ /* printf("%d, %s\n", r, strerror(errno)); */
return -1;
}
setsockopt(r, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(struct timespec));
@@ -106,12 +102,19 @@
sizeof(struct QUESTION),
0, (struct sockaddr*)&dest, sizeof(dest));
+ if (ret < 0) {
+ return 3;
+ }
+
clock_gettime(CLOCK_MONOTONIC, &start);
do {
ret = recvfrom(r, buf, 65535, 0, (struct sockaddr*)&dest, &dest_len);
clock_gettime(CLOCK_MONOTONIC, &end);
- if (!memcmp(&buf_send, buf, 100)) {
- printf("*1\n");
+ if (ret < 0) {
+ /* printf("*2, %d, %s\n", ret, strerror(errno)); */
+ break;
+ }
+ if ((ret = memcmp(&buf_send, buf + sizeof(struct ip) + sizeof(struct udphdr), sizeof(struct DNS_HEADER)))) {
break;
}
} while (start.tv_sec + 2 > end.tv_sec);
@@ -119,31 +122,13 @@
close(s);
close(r);
- printf("diff: %d\n", memcmp(&buf_send, buf, 100));
-
ip_head = (struct ip*)buf;
icmp_head = (struct icmphdr*)buf + sizeof(struct ip);
- for (int i = 0; i < 93; i++) {
- printf("%02X", buf[i]);
- }
- printf("\n");
-
- printf("len: %d, ver: %d, tos: %d, tlen: %d, ident: %d, ff: %d, ttl: %d, "
- "pro: %d, cs: %d, sip: %d, dip: %d\n",
- ip_head->ip_hl, ip_head->ip_v, ip_head->ip_tos, ip_head->ip_len,
- ip_head->ip_id, ip_head->ip_off, ip_head->ip_ttl, ip_head->ip_p,
- ip_head->ip_sum, ip_head->ip_src.s_addr, ip_head->ip_dst.s_addr);
-
- if (ip_head->ip_p != IP_UDP) {
- if (ip_head->ip_p == IP_ICMP) {
+ if (ip_head->ip_p != IPPROTO_UDP) {
+ if (ip_head->ip_p == IPPROTO_ICMP) {
return 1;
} else {
- printf("%d\n", ip_head->ip_p);
- for (int i = 0; i < sizeof(struct ip); i++) {
- printf("%02X", buf[i]);
- }
- printf("\n");
return 2;
}
}
--
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