From 96cf02139c7a0a344f194c95c8d3a64168e45c6b Mon Sep 17 00:00:00 2001
From: Joel Grunbaum <joelgrun@gmail.com>
Date: Wed, 01 Jun 2022 05:06:10 +0000
Subject: [PATCH] Compiler optimisations breaking things
---
dns.c | 152 +++++++++++++++++++++++++++++++++++++++-----------
1 files changed, 117 insertions(+), 35 deletions(-)
diff --git a/dns.c b/dns.c
index fb89c3a..c2053dd 100644
--- a/dns.c
+++ b/dns.c
@@ -1,17 +1,24 @@
+#include "dns.h"
#include <arpa/inet.h>
+#include <asm-generic/socket.h>
+#include <bits/time.h>
+#include <errno.h>
+#include <linux/if_ether.h>
+#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>
#include <sys/socket.h>
-//#include <netint/in.h>
-//#include <netdb.h>
-//#include <sys/time.h>
-#include "dns.h"
#include <time.h>
#include <unistd.h>
void change_to_DNS_name_format(unsigned char* dns, unsigned char* host);
char* read_name(unsigned char* reader, unsigned char* buffer, int* count);
+int fill_DNS_data(unsigned char* buf, int datasize, char* hostname,
+ int query_type);
// DNS code copied from
// https://gist.github.com/fffaraz/9d9170b57791c28ccda9255b48315168
@@ -64,16 +71,78 @@
char* rdata;
};
+// Test if an IP address is hosting a DNS server
+int reachable(unsigned char* buf, char* dns_ip)
+{
+ int s, r, ret, name_len;
+ struct sockaddr_in dest;
+ socklen_t dest_len = sizeof(dest);
+ struct timespec timeout, start, end;
+ struct icmphdr* icmp_head;
+ struct ip* ip_head;
+ unsigned char buf_send[65535];
+ timeout.tv_sec = 1;
+ timeout.tv_nsec = 0;
+
+ dest.sin_family = AF_INET;
+ dest.sin_port = htons(53);
+ dest.sin_addr.s_addr = inet_addr(dns_ip);
+
+ s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+ r = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL));
+ if (r < 0) {
+ /* printf("%d, %s\n", r, strerror(errno)); */
+ return -1;
+ }
+ setsockopt(r, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(struct timespec));
+
+ name_len = fill_DNS_data((unsigned char*)&buf_send, 65535, "google.com", T_A);
+ ret = sendto(s, buf_send,
+ sizeof(struct DNS_HEADER) + name_len + 1 +
+ 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 (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);
+
+ close(s);
+ close(r);
+
+ ip_head = (struct ip*)buf;
+ icmp_head = (struct icmphdr*)buf + sizeof(struct ip);
+
+ if (ip_head->ip_p != IPPROTO_UDP) {
+ if (ip_head->ip_p == IPPROTO_ICMP) {
+ return 1;
+ } else {
+ return 2;
+ }
+ }
+ return 0;
+}
+
// Test server dns_ip as IPv4 string for hostname
// Writes received packet to buf, which is supplied and returns time for request
struct timespec resolve(unsigned char* buf, char* hostname, char* dns_ip,
int query_type)
{
- int s, i;
+ int s, i, name_len;
struct sockaddr_in dest;
- unsigned char* qname;
- struct DNS_HEADER* dns = (struct DNS_HEADER*)buf;
- struct QUESTION* qinfo;
+ socklen_t dest_len = sizeof(dest);
struct timespec start, end, total, timeout;
timeout.tv_nsec = 0;
timeout.tv_sec = 1;
@@ -88,37 +157,13 @@
dest.sin_port = htons(53);
dest.sin_addr.s_addr = inet_addr(dns_ip);
- // dns packet header
- dns->id = (unsigned short)htons(getpid());
- dns->qr = 0; // make query
- dns->opcode = 0; // standard query
- dns->aa = 0; // not authoritive
- dns->tc = 0; // not trucated
- dns->rd = 1; // want recursion
- dns->ra = 0; // recursion not available
- dns->z = 0;
- dns->ad = 0;
- dns->cd = 0;
- dns->rcode = 0;
- dns->q_count = htons(1); // one question
- dns->ans_count = 0;
- dns->auth_count = 0;
- dns->add_count = 0;
-
- // dns packet query
- qname = (unsigned char*)&buf[sizeof(struct DNS_HEADER)];
- change_to_DNS_name_format(qname, (unsigned char*)hostname);
- qinfo = (struct QUESTION*)&buf[sizeof(struct DNS_HEADER) +
- strlen((const char*)qname) + 1];
- qinfo->qtype = htons(
- query_type); // type of query from argument (A,AAAA,MX,CNAME,NS,...)
- qinfo->qclass = htons(1); // internet class
+ name_len = fill_DNS_data(buf, 65535, hostname, query_type);
// send request
// return less than 0 is a fail
clock_gettime(CLOCK_MONOTONIC, &start);
i = sendto(s, (char*)buf,
- sizeof(struct DNS_HEADER) + strlen((const char*)qname) + 1 +
+ sizeof(struct DNS_HEADER) + name_len + 1 +
sizeof(struct QUESTION),
0, (struct sockaddr*)&dest, sizeof(dest));
@@ -127,7 +172,7 @@
// negative return is a fail
i = sizeof(dest);
i = recvfrom(s, (char*)buf, 65536, 0, (struct sockaddr*)&dest,
- (socklen_t*)&i);
+ &dest_len);
clock_gettime(CLOCK_MONOTONIC, &end);
}
@@ -321,3 +366,40 @@
name[i - 1] = '\0';
return name;
}
+
+// Populate the sending DNS packet with data
+int fill_DNS_data(unsigned char* buf, int datasize, char* hostname,
+ int query_type)
+{
+ struct DNS_HEADER* dns = (struct DNS_HEADER*)buf;
+ struct QUESTION* qinfo;
+ unsigned char* qname;
+
+ // dns packet header
+ dns->id = (unsigned short)htons(getpid());
+ dns->qr = 0; // make query
+ dns->opcode = 0; // standard query
+ dns->aa = 0; // not authoritive
+ dns->tc = 0; // not trucated
+ dns->rd = 1; // want recursion
+ dns->ra = 0; // recursion not available
+ dns->z = 0;
+ dns->ad = 0;
+ dns->cd = 0;
+ dns->rcode = 0;
+ dns->q_count = htons(1); // one question
+ dns->ans_count = 0;
+ dns->auth_count = 0;
+ dns->add_count = 0;
+
+ // dns packet query
+ qname = (unsigned char*)&buf[sizeof(struct DNS_HEADER)];
+ change_to_DNS_name_format(qname, (unsigned char*)hostname);
+ qinfo = (struct QUESTION*)&buf[sizeof(struct DNS_HEADER) +
+ strlen((const char*)qname) + 1];
+ qinfo->qtype = htons(
+ query_type); // type of query from argument (A,AAAA,MX,CNAME,NS,...)
+ qinfo->qclass = htons(1); // internet class
+
+ return strlen((const char*)qname);
+}
--
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