Panics on systems with empty /etc/resolv.conf #417
Description
While working on the Debian package of this project, I noticed a panic while running the testsuite of this package:
in Spec Setup (BeforeEach) [0.000 seconds]�[0m
dns add test
�[90m/<<PKGBUILDDIR>>/_build/src/github.com/containers/gvisor-tap-vsock/pkg/services/dns/dns_test.go:22�[0m
�[91m�[1mshould add dns zone with ip [BeforeEach]�[0m
�[90m/<<PKGBUILDDIR>>/_build/src/github.com/containers/gvisor-tap-vsock/pkg/services/dns/dns_test.go:29�[0m
�[91m�[1mTest Panicked�[0m
�[91mruntime error: index out of range [0] with length 0�[0m
/usr/lib/go-1.23/src/runtime/panic.go:115
�[91mFull Stack Trace�[0m
github.com/containers/gvisor-tap-vsock/pkg/services/dns.getDNSHostAndPort()
/<<PKGBUILDDIR>>/_build/src/github.com/containers/gvisor-tap-vsock/pkg/services/dns/dns_config_unix.go:15 +0x6c
github.com/containers/gvisor-tap-vsock/pkg/services/dns.newDNSHandler({0xbb0d80, 0x0, 0x0})
/<<PKGBUILDDIR>>/_build/src/github.com/containers/gvisor-tap-vsock/pkg/services/dns/dns.go:29 +0x37
github.com/containers/gvisor-tap-vsock/pkg/services/dns.New({0x0, 0x0}, {0x0, 0x0}, {0xbb0d80?, 0x10?, 0x1?})
/<<PKGBUILDDIR>>/_build/src/github.com/containers/gvisor-tap-vsock/pkg/services/dns/dns.go:166 +0x39
github.com/containers/gvisor-tap-vsock/pkg/services/dns.init.func1.1()
/<<PKGBUILDDIR>>/_build/src/github.com/containers/gvisor-tap-vsock/pkg/services/dns/dns_test.go:26 +0x33
github.com/containers/gvisor-tap-vsock/pkg/services/dns.TestSuite(0xc0000a8b60)
/<<PKGBUILDDIR>>/_build/src/github.com/containers/gvisor-tap-vsock/pkg/services/dns/dns_test.go:19 +0x3c
testing.tRunner(0xc0000a8b60, 0x8825b0)
/usr/lib/go-1.23/src/testing/testing.go:1690 +0xf4
created by testing.(*T).Run in goroutine 1
/usr/lib/go-1.23/src/testing/testing.go:1743 +0x390
�[90m------------------------------�[0m
�[91m�[1m•! Panic in Spec Setup (BeforeEach) [0.000 seconds]�[0m
This panic starts happening when upgrading to version 0.8.0. It does not occur with version 0.7.3
Looking at the code, I believe this is caused by 58eb054, which introduces
gvisor-tap-vsock/pkg/services/dns/dns_config_unix.go
Lines 9 to 17 in 72b102d
The panic occurs in line 15 when the test machine does have an empty /etc/resolv.conf. This makes sense for a build machine to attempt to disable connections to the internet.
Arguably, this can also happen outside of the test suite. Having the code raise an error seems preferable over a runtime error: index out of range [0] with length 0