Commit Graph

183 Commits (2708544018e4b8cdbc35ae8ae18398e3ccf69cbb)

Author SHA1 Message Date
David Anderson 15875ccc63 wgengine/router: don't store unused tunname on windows. 4 years ago
Brad Fitzpatrick e64383a80e wgengine/router: document some fields a bit more
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
David Anderson 2b4bfeda1a wgengine: pass in an explicit router.Router, rather than a generator.
Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 0a84aaca0a wgengine/router: remove unused wireguard *Device argument.
Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 672731ac6f many: gofmt.
Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 6521f02ff6 Move DNS flush logic to net/dns.
Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 9f7f2af008 wgengine/router/dns: move to net/dns.
Preparation for merging the APIs and whatnot.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 8432999835 Move wgengine/tsdns to net/dns.
Straight move+fixup, no other changes. In prep for merging with
wgengine/router/dns.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Brad Fitzpatrick e2b3d9aa5f all: s/Magic DNS/MagicDNS/ for consistency
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Brad Fitzpatrick 232cfda280 wgengine/router: report to control when setPrivateNetwork fails
Fixes #1503

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Brad Fitzpatrick d580b3f09e wgengine/router: fix go vet failure on BSDs
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Aleksandar Pesic 25d2dd868b wgengine/router: flushdns in windows when router config changes
Fixes: https://github.com/tailscale/tailscale/issues/1430

Signed-off-by: Aleksandar Pesic <peske.nis@gmail.com>
4 years ago
David Anderson fa6110e47b wgengine/router: don't touch interface routes
Developed by a cast of dozens.

Fixes #1448

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Denton Gentry 04e72f95cc wgengine/router: add OpenBSD IPv6 support.
Similar to FreeBSD in https://github.com/tailscale/tailscale/issues/1307,
add IPv6 addresses with a prefix length of 48.

Fixes https://github.com/tailscale/tailscale/issues/1372

Signed-off-by: Denton Gentry <dgentry@tailscale.com>
4 years ago
Denton Gentry bcea88da46 wgengine: support FreeBSD with IPv6.
Fixes https://github.com/tailscale/tailscale/issues/1307 for keepsies.

We cannot set the tun interface address as a /128 on FreeBSD,
due to https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=218508
Instead we set the interface address as a /48, which is enabled
by commit 82edf94df7.

Signed-off-by: Denton Gentry <dgentry@tailscale.com>
4 years ago
Denton Gentry c8af6bc009 Revert "freebsd: ignore IPv6 for now"
This reverts commit 061422affc.

We have a way to support IPv6 on FreeBSD now.

Signed-off-by: Denton Gentry <dgentry@tailscale.com>
4 years ago
Denton Gentry 061422affc freebsd: ignore IPv6 for now
FreeBSD tun devices don't work with the way we implement IPv6
https://github.com/tailscale/tailscale/issues/1307

At least for now, remove any IPv6 addresses from the netmap.

Signed-off-by: Denton Gentry <dgentry@tailscale.com>
4 years ago
David Anderson 1cb0ffc3ff wgengine/router: make windows gracefully handle disabled IPv4 or IPv6.
This is necessary because either protocol can be disabled globally by a
Windows registry policy, at which point trying to touch that address
family results in "Element not found" errors. This change skips programming
address families that Windows tell us are unavailable.

Fixes #1396.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 8d77dfdacb wgengine/router: add a dummy IPv6 address if needed for default routing.
Fixes #1339

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 793cb131f0 wgengine/router: toggle killswitch when using default routes on windows.
Fixes #1398.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 54d7070121 wgengine/router: correctly read IPv6 routes when diffing.
Fixes #1185.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Brad Fitzpatrick 2d96215d97 wgengine/router: make Linux delRoute idempotent, cidrDiff fail late as possible
This makes cidrDiff do as much as possible before failing, and makes a
delete of an already-deleted rule be a no-op. We should never do this
ourselves, but other things on the system can, and this should help us
recover a bit.

Also adds the start of root-requiring tests.

TODO: hook into wgengine/monitor and notice when routes are changed
behind our back, and invalidate our routes map and re-read from
kernel (via the ip command) at least on the next reconfig call.

Updates tailscale/corp#1338

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Brad Fitzpatrick 96a488e37e wgengine/router: simplify func normalizeCIDR using netaddr method 4 years ago
Brad Fitzpatrick 88ab0173a7 wgengine/router: fix BSD router to support multiple local addrs, IPv6
Fixes #1201
4 years ago
Brad Fitzpatrick 1ec64bc94d wgengine/router: add another Windows firewall rule to allow incoming UDP
Based on @sailorfrag's research.

Fixes #1312

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Brad Fitzpatrick d76334d2f0 ipn: split LocalBackend off into new ipn/ipnlocal package
And move a couple other types down into leafier packages.

Now cmd/tailscale doesn't bring in netlink, magicsock, wgengine, etc.

Fixes #1181

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Brad Fitzpatrick a2aa6cd2ed wgengine/router: clarify disabled IPv6 message on Linux 4 years ago
David Anderson 267531e4f8 wgengine/router: probe better for v6 policy routing support.
Previously we disabled v6 support if the disable_policy knob was
missing in /proc, but some kernels support policy routing without
exposing the toggle. So instead, treat disable_policy absence as a
"maybe", and make the direct `ip -6 rule` probing a bit more
elaborate to compensate.

Fixes #1241.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Brad Fitzpatrick c7fc4a06da wgengine/router: don't configure IPv6 on Linux when IPv6 is unavailable
Fixes #1214

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Brad Fitzpatrick 4fea604979 wgengine/router: stop setPrivateNetwork goroutine on configureInterface failure
On Windows, configureInterface starts a goroutine reconfiguring the
Windows firewall.

But if configureInterface fails later, that goroutine kept running and
likely failing forever, spamming logs. Make it stop quietly if its
launching goroutine filed.
4 years ago
Alex Brainman 6e4231c03c wgengine/router/dns: remove unused code
Commit 68ddf1 removed code that reads
`SOFTWARE\Tailscale IPN\SearchList` registry value. But the commit
left code that writes that value.

So now this package writes and never reads the value.

Remove the code to stop pointless work.

Updates #853

Signed-off-by: Alex Brainman <alex.brainman@gmail.com>
4 years ago
Brad Fitzpatrick 0d94fe5f69
wgengine/router: disable IPv6 on Linux if ip rule -6 fails (#1074)
Updates #562
Fixes #973

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Josh Bleecher Snyder 2fe770ed72 all: replace wgcfg.IP and wgcfg.CIDR with netaddr types
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
4 years ago
David Crawshaw 2b2a16d9a2 wgengine/router/dns: reduce windows registry key open timeout
The windows key timeout is longer than the wgengine watchdog timeout,
which means we never reach the timeout, instead the process exits.
Reduce the timeout so if we do hit it, at least the process continues.

Signed-off-by: David Crawshaw <crawshaw@tailscale.com>
4 years ago
David Crawshaw b4f70d8232 wgengine/router/dns: use the correct interface GUID
On Win10, there's a hardcoded GUID and this works.
On Win7, this GUID changes and we need to ask the tun for its
LUID and convert that from the GUID.

This commit uses the computed GUID that is placed in InterfaceName.

Diagnosed by Jason Donnenfeld. (Thanks!)
4 years ago
Brad Fitzpatrick 15c064f76f wgengine/router/dns: remove unsafe endianness detection on Linux 4 years ago
Brad Fitzpatrick f9659323df wgengine/router/dns: fix typo in comment 4 years ago
Brad Fitzpatrick 053a1d1340 all: annotate log verbosity levels on most egregiously spammy log prints
Fixes #924
Fixes #282

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Josh Bleecher Snyder 6db9c4a173 wgenginer/router/dns: use constant from golang.org/x/sys/windows
Made available in https://golang.org/cl/277153
4 years ago
Aleksandar Pesic 0dc295a640 Isolate WireGuard code into a separate file with appropriate copyright info in header.
Signed-off-by: Aleksandar Pesic <peske.nis@gmail.com>
4 years ago
Aleksandar Pesic d854fe95d2 Trivial change in function description.
Signed-off-by: Aleksandar Pesic <peske.nis@gmail.com>
4 years ago
Aleksandar Pesic 338fd44657 Replace registry-access code, update wireguard-go and x/sys/windows.
Signed-off-by: Aleksandar Pesic <peske.nis@gmail.com>
4 years ago
Aleksandar Pesic 274d32d0aa Prepare for the new wireguard-go API.
Signed-off-by: Aleksandar Pesic <peske.nis@gmail.com>
4 years ago
Brad Fitzpatrick fc8bc76e58 wgengine/router: lock goroutine to OS thread before using OLE [windows]
See https://github.com/tailscale/tailscale/issues/921#issuecomment-727526807

Not yet sure whether this is our problem, but it can't hurt at least,
and seems like what we're supposed to do.

Updates #921
4 years ago
David Anderson a664aac877 wgengine/router: disable IPv6 if v6 policy routing is unavailable.
Fixes #895.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson ebd96bf4a9 wgengine/router/dns: use OpenKeyWait to set DNS configuration.
Fixes tailscale/corp#839.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Brad Fitzpatrick 119101962c wgengine/router: don't double-prefix dns log messages [Windows] 4 years ago
Brad Fitzpatrick 28f6552646 wgengine/router/dns: run ipconfig /registerdns async, log timing
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Brad Fitzpatrick 01ee638cca Change some os.IsNotExist to errors.Is(err, os.ErrNotExist) for non-os errors.
os.IsNotExist doesn't unwrap errors. errors.Is does.

The ioutil.ReadFile ones happened to be fine but I changed them so
we're consistent with the rule: if the error comes from os, you can
use os.IsNotExist, but from any other package, use errors.Is.
(errors.Is always would also work, but not worth updating all the code)

The motivation here was that we were logging about failure to migrate
legacy relay node prefs file on startup, even though the code tried
to avoid that.

See golang/go#41122
4 years ago
David Anderson 68ddf134d7 wgengine/router/dns: issue ipconfig /registerdns when applying DNS settings.
Amazingly, there doesn't seem to be a documented way of updating network
configuration programmatically in a way that Windows takes notice of.
The naturopathic remedy for this is to invoke ipconfig /registerdns, which
does a variety of harmless things and also invokes the private API that
tells windows to notice new adapter settings. This makes our DNS config
changes stick within a few seconds of us setting them.

If we're invoking a shell command anyway, why futz with the registry at
all? Because netsh has no command for changing the DNS suffix list, and
its commands for setting resolvers requires parsing its output and
keeping track of which server is in what index. Amazingly, twiddling
the registry directly is the less painful option.

Fixes #853.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Brad Fitzpatrick 508f5c3ae0 wgengine/router: fix bug where getInterfaceRoutes always returned an empty list
Regression from f2ce64f0c6 (r43710860)

Fixes #870
4 years ago
Brad Fitzpatrick 38bde61b3d wgengine/router: make Windows firewall configuration async
Updating the Windows firewall is usually reasonably fast, but
sometimes blocks for 20 seconds, 4 minutes, etc. Not sure why.

Until we understand that's happening, configure it in the background
without blocking the normal control flow.

Updates #785

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
David Anderson ff0cf6340a wgengine/router: fix configuration of loopback netfilter rules for v6.
Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Alex Brainman f2ce64f0c6 wgengine/router: unfork winipcfg-go package, use upstream
Use golang.zx2c4.com/wireguard/windows/tunnel/winipcfg
instead of github.com/tailscale/winipcfg-go package.

Updates #760

Signed-off-by: Alex Brainman <alex.brainman@gmail.com>
4 years ago
David Anderson c493e5804f wgengine/router: make v6-ness configurable in test, for consistent results.
Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Brad Fitzpatrick c86761cfd1 Remove tuntap references. We only use TUN. 4 years ago
Brad Fitzpatrick bbb56f2303 wgengine/router: fix tests on Debian Buster as regular user on machine with IPv6 4 years ago
David Anderson fddbcb0c7b wgengine/router: support various degrees of broken IPv6.
Gracefully skips touching the v6 NAT table on systems that don't have
it, and doesn't configure IPv6 at all if IPv6 is globally disabled.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 0d80904fc2 wgengine/router: set up basic IPv6 routing/firewalling.
Part of #19.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Brad Fitzpatrick 2d0ed99672 wgengine, wgengine/router: add a bunch of (temporary?) engine creation logging
Trying to debug what's slow on a user's machine.

Updates #785
4 years ago
Brad Fitzpatrick 7c11f71ac5 wgengine/router: ignore errors deleting 169.254.255.255/32 route on Windows
Updates #785
4 years ago
Brad Fitzpatrick 3528d28ed1 wgengine/router: move Tailscale's winipcfg additions into wgengine/router
Part of unforking our winipcfg-go and using upstream (#760), move our
additions into our repo. (We might upstream them later if upstream has
interest)

Originally these were:

@apenwarr: "Add ifc.SyncAddresses() and SyncRoutes()."
609dcf2df5

@bradfitz: "winipcfg: make Interface.AddRoutes do as much as possible, return combined error"
e9f93d53f3

@bradfitz: "prevent unnecessary Interface.SyncAddresses work; normalize IPNets in deltaNets"
decb9ee8e1
4 years ago
Brad Fitzpatrick fd77268770 wgengine/router: enumerate all interfaces when finding Tailscale adapter by GUID
Might fix it. I've spent too much time failing to reproduce the issue. This doesn't
seem to make it worse, though (it still runs for me), so I'll include this and
see if it helps others while I still work on a reliable way to reproduce it.

Updates tailscale/corp#474
4 years ago
Brad Fitzpatrick 5bcac4eaac net/tshttpproxy: add GetProxyForURL negative cache
Otherwise when PAC server is down, we log, and each log entry is a new
HTTP request (from logtail) and a new GetProxyForURL call, which again
logs, non-stop. This is also nicer to the WinHTTP service.

Then also hook up link change notifications to the cache to reset it
if there's a chance the network might work sooner.
4 years ago
Christina Wen f0e9dcdc0a
wgengine/router: restore /etc/resolv.conf after tailscale down is called
This change is to restore /etc/resolv.conf after tailscale down is called. This is done by setting the dns.Manager before errors occur. Error collection is also added.

Fixes #723
4 years ago
Brad Fitzpatrick acafe9811f wgengine/router: run netsh advfirewall less, rename, document setFirewall 4 years ago
Christina Wen e862f90e34
wgengine/router/router_linux.go: fixed " route del failed" error (#756)
* wgengine/router/router_linux.go: Switched `cidrDiff("addr")` and `cidrDiff("route")` order

Signed-off-by: Christina Wen <christina@tailscale.com>

Co-authored-by: Christina Wen <christina@tailscale.com>
4 years ago
Brad Fitzpatrick 7e9d1f7808 wgengine/router: tighten isMissingIPv6Err
So it doesn't false positive if misused.

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
David Anderson 8f5b52e571 net/netns: add windows support.
Also remove rebinding logic from the windows router. Magicsock will
instead rebind based on link change signals.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Brad Fitzpatrick a084c44afc wgengine, wgengine/router, cmd/tailscale: force netfilter mode off on Synology
For now. Get it working again so it's not stuck on 0.98.

Subnet relay can come later.

Updates #451

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Brad Fitzpatrick 31c13013ae wgengine/router: tolerate disabled IPv6 on Windows
Fixes #412
Updates #524 (maybe fixes?)

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Josh Bleecher Snyder 37b40b035b wgengine/router/dns: appease staticcheck (again) 4 years ago
Josh Bleecher Snyder a877dd575c wgengine/router/dns: remove unnecessary lint ignore line
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
4 years ago
Brad Fitzpatrick 913c1bd04f wgengine/router: on Windows, add a firewall rule to allow Tailscale
Updates tailscale/tailscale#454
4 years ago
Brad Fitzpatrick 6d14678009 wgengine/router: remove unnecessary newlines in log.Printf formats 4 years ago
Brad Fitzpatrick 09d56f54a7
wgengine/router: fix Windows route sorting that caused de-dup to not work (#727)
Updates #725

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Dmytro Shynkevych a903d6c2ed
tailcfg, tsdns: derive root domains from list of nodes (#708)
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Brad Fitzpatrick 461db356b9 wgengine/router/dns: fix staticcheck error on Mac 4 years ago
Dmytro Shynkevych a583e498b0
router/dns: set all domains on Windows (#672)
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Mike Kramlich 6fa7a9a055 wgengine/router/router_userspace_bsd: on Mac the route program syntax expects delete not del -- this had caused router reconfig to fail in some cases. Fixes #673
Signed-off-by: Mike Kramlich <groglogic@gmail.com>
4 years ago
Dmytro Shynkevych 95a18f815c
router/dns: detect host endianness for NetworkManager.
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Brad Fitzpatrick c64a43a734 wgengine/router: set MTU on Windows to min(configured,possible)
Fixes tailscale/corp#542

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
4 years ago
Josh Bleecher Snyder 2622e8e082 wgenginer/router: fix build
Rebasing github.com/tailscale/wireguard-go to upstream
wireguard-go changed the API.

This commit is analogous to
https://git.zx2c4.com/wireguard-windows/commit/?id=6823cc10ffe193c0cb1d61a5d1828d563d3d0e5f
4 years ago
Dmytro Shynkevych 28e52a0492
all: dns refactor, add Proxied and PerDomain flags from control (#615)
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Dmytro Shynkevych 8c850947db
router: split off sandboxed path from router_darwin (#624)
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Dmytro Shynkevych 2ce2b63239
router: stop iOS subprocess sandbox violations (#617)
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Dmytro Shynkevych 154d1cde05
router: reload systemd-resolved after changing /etc/resolv.conf (#619)
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Dmytro Shynkevych c53ab3111d wgengine/router: support legacy resolvconf
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
David Anderson 189d86cce5 wgengine/router: don't use 88 or 8888 as table/rule numbers.
We originally picked those numbers somewhat at random, but with the idea
that 8 is a traditionally lucky number in Chinese culture. Unfortunately,
"88" is also neo-nazi shorthand language.

Use 52 instead, because those are the digits above the letters
"TS" (tailscale) on a qwerty keyboard, so we're unlikely to collide with
other users. 5, 2 and 52 are also pleasantly culturally meaningless.

Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson 972a42cb33 wgengine/router: fix router_test to match the new marks.
Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
David Anderson d60917c0f1 wgengine/router: switch packet marks to avoid conflict with Weave Net.
Signed-off-by: David Anderson <danderson@tailscale.com>
4 years ago
Dmytro Shynkevych a3e7252ce6 wgengine/router: use better NetworkManager API
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Eduardo Kienetz 5df6be9d38 Use LittleEndian for correct byte order on DNS IPs
Nameserver IP 10.11.12.13 would otherwise get written to resolv.conf as 13.12.11.10, as was happening on my client.

Signed-off-by: Eduardo Kienetz <eduardo@kienetz.com>
4 years ago
Wendi Yu c3736250a4
wgengine: fix macos staticcheck errors (#557)
Signed-off-by: Wendi <wendi.yu@yahoo.ca>
4 years ago
Dmytro Shynkevych 30bbbe9467
wgengine/router: dns: unify on *BSD, multimode on Linux, Magic DNS (#536)
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Dmytro Shynkevych 61abab999e
cmd/tailscaled: graceful shutdown (#534)
Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
4 years ago
Brad Fitzpatrick 742b8b44a8 net/tsaddr: new package to hold Tailscale-specific IPs/ranges
And update existing callers with (near) duplicated cases.
4 years ago
David Crawshaw 9258d64261 wgengine/router: do not call ifconfig up if SetRoutesFunc is set
The NetworkExtension brings up the interface itself and does not have
access to `ifconfig`, which the underlying BSD userspace router attempts
to use when Up is called.

Signed-off-by: David Crawshaw <crawshaw@tailscale.com>
4 years ago
Reinaldo de Souza a8635784bc wgengine: add BSD userspace router to darwin
Darwin and FreeBSD are compatible enough to share the userspace router.

The OSX router delegates to the BSD userspace router unless `SetRoutesFunc` is set.
That preserves the mechanism that allows `ipn-go-bridge` to specify its own routing behavior.

Fixes #177

Signed-off-by: Reinaldo de Souza <github@rei.nal.do>
4 years ago
David Anderson 5a32f8e181 wgengine/router: also accept exit code 254 from `ip rule del`.
iproute2 3.16.0-2 from Debian Jessie (oldoldstable) doesn't return
exit code 2 when deleting a non-existent IP rule.

Fixes #434

Signed-off-by: David Anderson <danderson@tailscale.com>
5 years ago