error: TemporaryNameServerFailure when using package management on Termux

[leap0x7b]

Zig Version

0.11.0-dev.1606+3c2a43fdc

Steps to Reproduce and Observed Behavior

1. Create a Zig project using either zig init-lib or zig init-exe
2. Create a build.zig.zon file:

.{
    .name = "viisi",
    .description = "A RISC-V hobby computer inspired by old 80s/90s UNIX workstations",
    .version = "0.1.0",
    .dependencies = .{
        .clap = .{
            .url = "https://github.com/Hejsil/zig-clap/archive/272d8e2088b2cae037349fb260dc05ec46bba422.tar.gz",
        },
    },
}

3. Run zig build

Expected Behavior

It should be able to resolve github.com and download the file.

[hryx]

I'm also getting this on Arch Linux with systemd-networkd and systemd-resolved. Working just fine on macOS though. Not sure if this helps but:

$ strace --trace=network zig build test
socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 8
bind(8, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
sendto(8, "1\334\1\0\0\1\0\0\0\0\0\0\6github\3com\0\0\1\0\1", 28, MSG_NOSIGNAL, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 16) = 28
sendto(8, "2\245\1\0\0\1\0\0\0\0\0\0\6github\3com\0\0\34\0\1", 28, MSG_NOSIGNAL, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 16) = 28
sendto(8, "1\334\1\0\0\1\0\0\0\0\0\0\6github\3com\0\0\1\0\1", 28, MSG_NOSIGNAL, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 16) = 28
sendto(8, "2\245\1\0\0\1\0\0\0\0\0\0\6github\3com\0\0\34\0\1", 28, MSG_NOSIGNAL, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 16) = 28
error: TemporaryNameServerFailure
+++ exited with 1 +++

[andrewrk]

A related issue, #14900, was solved recently. Did it solve this issue as well?

[hryx]

I see a different error now, error.ConnectionFailed. The strace output looks identical to before. Let me know if there are any better diagnostics I can provide.

[leap0x7b]

Still doesn't work, I also got error.ConnectionFailed as well

[hryx]

I went to debug this by altering std.http.Client, but got a strange result before I even changed any code.

I checked out 602029b (commit of latest release at the time of this test), build stage3 (Release) and stage4 (Debug), and ran zig build on a project with dependencies, making sure to clear the global package cache between runs. Both of those built zig executables successfully fetched deps.

But I downloaded the official release with the same commit hash and got error.ConnectionFailed as before. I would run the official build through a debugger but of course it is stripped, so I'm trying to think of a next step.

[mikdusan]

@hryx,

just to rule it out, does this run without error?

const std = @import("std");

pub fn main() !void {
    var general_purpose_allocator = std.heap.GeneralPurposeAllocator(.{}){};
    const gpa = general_purpose_allocator.allocator();

    var http_client: std.http.Client = .{ .allocator = gpa };
    defer http_client.deinit();

    const uri = try std.Uri.parse("http://github.com");
    var req = try http_client.request(uri, .{}, .{});
    defer req.deinit();
}

[hryx]

@mikdusan It does not! Good idea to test by using an HTTP client directly.

Error output:

error: ConnectionFailed
/home/hryx/lib/std/net.zig:45:9: 0x46a95a in parseIp (main)
        return error.InvalidIPAddressFormat;
        ^
/home/hryx/lib/std/net.zig:75:29: 0x46a549 in parseExpectingFamily (main)
            os.AF.UNSPEC => return parseIp(name, port),
                            ^
/home/hryx/lib/std/net.zig:1414:48: 0x476584 in linuxLookupNameFromDns (main)
    if (ap[0].len < 4 or (ap[0][3] & 15) == 2) return error.TemporaryNameServerFailure;
                                               ^
/home/hryx/lib/std/net.zig:1358:5: 0x4778ec in linuxLookupNameFromDnsSearch (main)
    return linuxLookupNameFromDns(addrs, canon, name, family, rc, port);
    ^
/home/hryx/lib/std/net.zig:996:17: 0x4785e7 in linuxLookupName (main)
                try linuxLookupNameFromDnsSearch(addrs, canon, name, family, port);
                ^
/home/hryx/lib/std/net.zig:933:9: 0x428661 in getAddressList (main)
        try linuxLookupName(&lookup_addrs, &canon, name, family, flags, port);
        ^
/home/hryx/lib/std/net.zig:709:18: 0x35685f in tcpConnectToHost (main)
    const list = try getAddressList(allocator, name, port);
                 ^
/home/hryx/lib/std/http/Client.zig:896:9: 0x3209ac in connect (main)
        return error.ConnectionFailed;
        ^
/home/hryx/lib/std/http/Client.zig:994:23: 0x30f194 in request (main)
        .connection = try client.connect(host, port, protocol),
                      ^
/home/hryx/tmp/issue14636/main.zig:11:15: 0x30e942 in main (main)
    var req = try http_client.request(uri, .{}, .{});
              ^

I added a log right before the error return in linuxLookupNameFromDns with the values of ap:

info: ap0: 7c8f850200010000000000000667697468756203636f6d0000010001 = githubcom
info: ap1: 7f20850200010000000000000667697468756203636f6d00001c0001 = Tgithubcom

[hryx]

I fixed the issue on my machine. I'll report what I found in case it helps @leap0x7b or others, but I'm left to speculate about the original root cause.

The issue was mundane: my /etc/resolv.conf was supposed to be a symlink to /run/systemd/resolve/stub-resolv.conf, but it was a plain file. When systemd-resolved is used, it needs to be a link to the stub file. The solution was to remove /etc/resolv.conf and make it a link, but it could probably also be solved by reinstalling the relevant package.

My guess is that my system got into a bad state long ago but didn't show symptoms until the Zig HTTP client tried to resolve DNS by reading resolv.conf directly. It was an empty file (except for a comment), so name resolution obviously failed. I don't understand why every other program was still able to use DNS — maybe glibc falls back to discovering a local nameserver, while musl doesn't. In fact, Zig built locally with glibc was able to make these HTTP requests, even with my previously bad system state.

As for how my system got into that state, who knows, but I have had at least one service that modifies /etc/resolv.conf, and it could have been a since-fixed bug in the service or even package install script. I wasn't able to reproduce the issue after reinstalling Tailscale and NetworkManager, for example.

Anyway, no Zig bug here as far as I am concerned.

[pfgithub]

On Android (termux), /etc/resolv.conf doesn't exist

const std = @import("std");

pub fn main() !void {
    var general_purpose_allocator = std.heap.GeneralPurposeAllocator(.{}){};
    const gpa = general_purpose_allocator.allocator();

    var http_client: std.http.Client = .{ .allocator = gpa };
    defer http_client.deinit();

    const uri = try std.Uri.parse("http://github.com");
    var req = try http_client.request(.GET, uri, .{
        .allocator = gpa,
    }, .{});
    defer req.deinit();
}

openat(AT_FDCWD, "/etc/resolv.conf", O_RDONLY|O_NOCTTY|O_LARGEFILE|O_CLOEXEC) = -1 ENOENT (No such file or directory)

wget and other programs work fine

$PREFIX/etc/resolv.conf does exist (/data/data/com.termux/files/usr/etc/resolv.conf)

Packages in the termux package manager have to patch this folder it seems: https://github.com/termux/termux-packages/pull/14738/files

Applying these patches to std/net.zig appears to fix the issue for using http_client.request, but zig would have to be recompiled with these changes to fix zig build:

-   const file = fs.openFileAbsoluteZ("/etc/hosts", .{}) catch |err| switch (err) {
+   const file = fs.openFileAbsoluteZ("/data/data/com.termux/files/usr/etc/hosts", .{}) catch |err| switch (err) {
-   const file = fs.openFileAbsoluteZ("/etc/resolv.conf", .{}) catch |err| switch (err) {
+   const file = fs.openFileAbsoluteZ("/data/data/com.termux/files/usr/etc/resolv.conf", .{}) catch |err| switch (err) {

I'm not sure what to do about this?

• Termux can't put things in the standard locations because of android restrictions: https://wiki.termux.com/wiki/Differences_from_Linux
• Zig wants to ship static binaries that can run on any linux machine, but any zig application that accesses the internet will need to be rebuilt and packaged for termux to fix the hardcoded locations of these system files

Some possible solutions:

• Do nothing, require termux users to install zig from the system package manager or build it themselves. Binaries built with zig for linux are only for distros conforming to the Filesystem Hierarchy Standard
  • This doesn't seem ideal, zig from package managers is often at least six months out of date
• Use $PREFIX and change the paths for /etc/resolv.conf and /etc/hosts
  • Similar to Use $PREFIX to resolve /usr/bin/env #15896 but $PREFIX would have to be preferred - android has its own /etc/hosts file when termux's should be used instead
  • Is $PREFIX any kind of standard environment variable? Will some people have this set for a different reason and this change would cause undesired behaviour for them?
• Require a special environment variable to be set to request different locations for these system files
• Something else

[truemedian]

Until the problem is solved in zig, the likely temporary solution seems to be laid out in the https://wiki.termux.com/wiki/Differences_from_Linux that you linked. You can use termux-chroot from proot to get back FHS compliance for now.