From 3c8e230ee1ea856742647d5e1e79087f100eb01b Mon Sep 17 00:00:00 2001 From: David Anderson Date: Thu, 6 May 2021 22:30:26 -0700 Subject: [PATCH] Revert "net/dns: set IPv4 auto mode in NM, so it lets us set DNS." This reverts commit 7d16c8228bcf70a3b82afe994e8c5fa42057c5f3. I have no idea how I ended up here. The bug I was fixing with this change fails to reproduce on Ubuntu 18.04 now, and this change definitely does break 20.04, 20.10, and Debian Buster. So, until we can reliably reproduce the problem this was meant to fix, reverting. Part of #1875 Signed-off-by: David Anderson --- net/dns/nm.go | 34 ++++++++++++---------------------- 1 file changed, 12 insertions(+), 22 deletions(-) diff --git a/net/dns/nm.go b/net/dns/nm.go index 29f0f2205..5ba3130b7 100644 --- a/net/dns/nm.go +++ b/net/dns/nm.go @@ -183,25 +183,6 @@ func (m *nmManager) trySet(ctx context.Context, config OSConfig) error { // settings here, but that led to #1870. ipv4Map := settings["ipv4"] - // In some versions of NM, you can only provide DNS configuration - // if the interface is in "auto" or "manual" mode (defaults to - // "disabled"). - // - // In "manual" mode we'd have to also give NM all our IP and - // routing configuration, which we don't want to do. So instead, - // we set the ipv4 mode to "auto", and then tell it to ignore any - // information it might get from DHCP (which is none, since we - // don't do DHCP on tailscale0). This is the documented way to - // provide only DNS configuration to NetworkManager. - // - // Some versions of NM don't need this, and will accept DNS - // configuration even for disabled interfaces, but there's no harm - // in telling those versions to do DHCP and ignore all results, - // hence why we have a single codepath here. - ipv4Map["method"] = dbus.MakeVariant("auto") - ipv4Map["ignore-auto-routes"] = dbus.MakeVariant(true) - ipv4Map["ignore-auto-dns"] = dbus.MakeVariant(true) - ipv4Map["never-default"] = dbus.MakeVariant(true) ipv4Map["dns"] = dbus.MakeVariant(dnsv4) ipv4Map["dns-search"] = dbus.MakeVariant(search) // We should only request priority if we have nameservers to set. @@ -221,9 +202,18 @@ func (m *nmManager) trySet(ctx context.Context, config OSConfig) error { } ipv6Map := settings["ipv6"] - // Same logic as above for IPv4 - request autoconfiguration, tell - // NM to ignore all autoconfiguration results, and provide manual - // DNS settings. + // In IPv6 settings, you're only allowed to provide additional + // static DNS settings in "auto" (SLAAC) or "manual" mode. In + // "manual" mode you also have to specify IP addresses, so we use + // "auto". + // + // NM actually documents that to set just DNS servers, you should + // use "auto" mode and then set ignore auto routes and DNS, which + // basically means "autoconfigure but ignore any autoconfiguration + // results you might get". As a safety, we also say that + // NetworkManager should never try to make us the default route + // (none of its business anyway, we handle our own default + // routing). ipv6Map["method"] = dbus.MakeVariant("auto") if len(addrs6) > 0 { ipv6Map["address-data"] = dbus.MakeVariant(addrs6)