Hi,
When resolving some hostnames, gethostbyname is broken on Linux. This doesn’t affect only the Linux client, since I was able to reproduce the issue from a Docker container running on a Windows host which was running WARP. The getaddrinfo function is not affected by this bug.
To test this, run python3 -c "import socket; print(socket.gethostbyname('test.s3.amazonaws.com'))". When WARP is running, the following exception is raised:
Traceback (most recent call last):
File "<string>", line 1, in <module>
socket.gaierror: [Errno -5] No address associated with hostname
When testing gethostbyname natively from C, the error is NO_RECOVERY. The man page says A nonrecoverable name server error occurred.. I checked the source code for this and there’s a number of reasons this error could occur and I couldn’t figure out the exact cause.
// TEST C CODE FOR WARP DOH ERRORS
#include <netdb.h>
#include <stdio.h>
#include <unistd.h>
#include <limits.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
int main(int argc, char* argv[])
{
struct hostent* host = gethostbyname("test.s3.amazonaws.com");
if (!host) {
printf("error %d \n", h_errno);
switch (h_errno) {
case HOST_NOT_FOUND:
printf("HOST_NOT_FOUND\n");
break;
case NO_DATA:
printf("NO_DATA\n");
break;
case NO_RECOVERY:
printf("NO_RECOVERY\n");
break;
case TRY_AGAIN:
printf("TRY_AGAIN\n");
break;
default:
printf("unknown\n");
}
} else {
printf ("Name: %s \n", host->h_name);
char* alias = host->h_aliases[0];
while (alias) {
printf ("\tAlias: %s \n", alias);
alias++;
break;
}
}
struct addrinfo hints = {}, *addrs;
hints.ai_flags = AI_CANONNAME;
char port_str[16] = {};
int err = getaddrinfo("test.s3.amazonaws.com", port_str, &hints, &addrs);
if (err != 0)
{
fprintf(stderr, " %s\n", gai_strerror(err));
} else {
char* address[24];
inet_ntop(AF_INET, &(((struct sockaddr_in *)addrs->ai_addr)->sin_addr), address, 24);
printf("addr: %s\ncannonname: %s\n", address, addrs->ai_canonname);
}
}
This also breaks getent hosts test.s3.amazonaws.com which returns no results.
Anyone else experiencing this issue? This makes WARP DoH absolutely unusable on Linux.