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
---
test.c | 40 +++++++------
slist.c | 20 +++++-
main.c | 40 +++++++++++-
dns.c | 41 ++++---------
4 files changed, 85 insertions(+), 56 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;
}
}
diff --git a/main.c b/main.c
index 780bb36..9787a55 100644
--- a/main.c
+++ b/main.c
@@ -24,7 +24,7 @@
// Variables are only modified before threads are created and as such are
// thread-safe tests_done is modified to provide a rough count of number of
// tests being completed for progress measurement
-int tests_done = 0, num_tests = NUM_TESTS, num_servers = NUM_DNS, num_hosts = 0;
+int tests_done = 0, num_tests = NUM_TESTS, num_servers = 0, num_hosts = 0;
struct hosts_list* hosts = NULL;
struct dns_list* servers = NULL;
@@ -76,6 +76,7 @@
}
for (int i = 0; i < NUM_DNS; i++) {
add_dns_server(&servers, (char*)DNS_SERVERS[i]);
+ num_servers++;
}
test_dns();
sort_servers(&servers);
@@ -92,13 +93,43 @@
{
struct dns_list* curr = servers;
int i = 0;
- pthread_t* threads = malloc(num_servers * sizeof(pthread_t));
+ int init_num_servers = num_servers;
+ pthread_t* threads;
pthread_t progress;
+ // Check each server for reachability, can't be done in parallel as incorrect packets are received
+ // reachable() requires raw packets, which needs root
+ if (getuid() == 0) {
+ while (curr) {
+ printf("\rTesting reachability: %d/%d", i, init_num_servers); fflush(stdout);
+ unsigned char* buf[65535];
+ int error_count = 0;
+ curr->errors = 0;
+ // retry 10 times for UDP unreliability
+ for (int i = 0; i < 10; i++) {
+ error_count += (reachable((unsigned char*)buf, curr->server) != 0);
+ }
+ /* fprintf(stderr, "ip: %s, ec: %d\n", curr->server, error_count); */
+ // 30% error rate means unreachable
+ if (error_count >= 3) {
+ curr->errors = -1;
+ num_servers--;
+ }
+ curr = curr->next;
+ i++;
+ }
+ printf("\rTesting reachability: %d/%d\n", i, init_num_servers);
+ }
+
+ threads = malloc(num_servers * sizeof(pthread_t));
+ curr = servers;
+ i = 0;
pthread_create(&progress, NULL, print_progress, NULL);
while (curr) {
- pthread_create(&threads[i], NULL, test_server, (void*)curr);
+ if (curr->errors == 0) {
+ pthread_create(&threads[i], NULL, test_server, (void*)curr);
+ i++;
+ }
curr = curr->next;
- i++;
}
for (int i = 0; i < num_servers; i++) {
pthread_join(threads[i], NULL);
@@ -116,7 +147,6 @@
struct dns_list* dns = (struct dns_list*)in;
dns->time.tv_sec = 0;
dns->time.tv_nsec = 0;
- dns->errors = 0;
for (int i = 0; i < num_tests; i++) {
struct hosts_list* curr = hosts;
while (curr) {
diff --git a/slist.c b/slist.c
index 5deefc9..971685f 100644
--- a/slist.c
+++ b/slist.c
@@ -130,11 +130,23 @@
int print_servers(struct dns_list* head)
{
+ struct dns_list* curr = head;
printf("%-16s | %-11s | %s\n", "Server", "Time", "Errors");
- while (head) {
- printf("%-16s | %ld.%09ld | %d\n", head->server, head->time.tv_sec,
- head->time.tv_nsec, head->errors);
- head = head->next;
+ while (curr) {
+ if (curr->errors != -1) {
+ printf("%-16s | %ld.%09ld | %d\n", curr->server, curr->time.tv_sec,
+ curr->time.tv_nsec, curr->errors);
+ }
+ curr = curr->next;
}
+ fflush(stdout);
+ curr = head;
+ if (head->errors == -1) {
+ printf("The following servers were unreachable:\n");
+ while (curr && curr->errors == -1) {
+ printf("%s\n", curr->server);
+ curr = curr->next;
+ }
+ }
return 0;
}
diff --git a/test.c b/test.c
index 7ddbf1c..aae2c20 100644
--- a/test.c
+++ b/test.c
@@ -6,25 +6,27 @@
int main(void)
{
- char* hostname = "google.com";
- char* IP = "127.0.0.1";
- int type = T_A;
unsigned char buf[65536];
- struct timespec ret;
- int r;
+ int error_count;
- r = reachable(buf, "10.0.0.0");
- printf("%d\n", r);
- /* print_packet(buf + sizeof(struct ip)); */
- r = reachable(buf, "127.0.0.2");
- printf("%d\n", r);
-
- /* ret = resolve(buf, hostname, IP, type); */
-
- /* printf("%ld, %ld\n", ret.tv_sec, ret.tv_nsec); */
-
- /* print_packet(buf); */
- /* for (int i = 0; i < 98; i++) { */
- /* printf("%X", buf[i]); */
- /* } */
+ error_count = 0;
+ for (int i = 0; i < 100; i++) {
+ error_count += (reachable(buf, "1.1.1.1") != 0);
+ }
+ printf("1.1.1.1: %d\n", error_count);
+ error_count = 0;
+ for (int i = 0; i < 100; i++) {
+ error_count += (reachable(buf, "192.168.0.101") != 0);
+ }
+ printf("192.168.0.101: %d\n", error_count);
+ error_count = 0;
+ for (int i = 0; i < 100; i++) {
+ error_count += (reachable(buf, "192.168.0.100") != 0);
+ }
+ printf("192.168.0.100: %d\n", error_count);
+ error_count = 0;
+ for (int i = 0; i < 100; i++) {
+ error_count += (reachable(buf, "129.146.153.226") != 0);
+ }
+ printf("129.146.153.226: %d\n", error_count);
}
--
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