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tailscale/net
Andrea Gottardo d9aeb30281
net/interfaces: handle iOS network transitions (#10680)
Updates #8022
Updates #6075

On iOS, we currently rely on delegated interface information to figure out the default route interface.  The NetworkExtension framework in iOS seems to set the delegate interface only once, upon the *creation* of the VPN tunnel. If a network transition (e.g. from Wi-Fi to Cellular) happens while the tunnel is connected, it will be ignored and we will still try to set Wi-Fi as the default route because the delegated interface is not getting updated as connectivity transitions.

Here we work around this on the Swift side with a NWPathMonitor instance that observes the interface name of the first currently satisfied network path. Our Swift code will call into `UpdateLastKnownDefaultRouteInterface`, so we can rely on that when it is set.

If for any reason the Swift machinery didn't work and we don't get any updates, here we also have some fallback logic: we try finding a hardcoded Wi-Fi interface called en0. If en0 is down, we fall back to cellular (pdp_ip0) as a last resort. This doesn't handle all edge cases like USB-Ethernet adapters or multiple Ethernet interfaces, but it is good enough to ensure connectivity isn't broken.

I tested this on iPhones and iPads running iOS 17.1 and it appears to work. Switching between different cellular plans on a dual SIM configuration also works (the interface name remains pdp_ip0).

Signed-off-by: Andrea Gottardo <andrea@tailscale.com>
11 months ago
..
art all: cleanup unused code, part 2 (#10670) 11 months ago
connstats net/connstats: exclude traffic with internal Tailscale service (#7904) 2 years ago
dns all: cleanup unused code, part 2 (#10670) 11 months ago
dnscache all: cleanup unused code, part 2 (#10670) 11 months ago
dnsfallback net/dnsfallback: add singleflight to recursive resolver 1 year ago
flowtrack all: update copyright and license headers 2 years ago
interfaces net/interfaces: handle iOS network transitions (#10680) 11 months ago
memnet net/memnet: export the network name (#9111) 1 year ago
netaddr all: update copyright and license headers 2 years ago
netcheck net/netcheck: use DERP frames as a signal for home region liveness 12 months ago
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netknob all: update copyright and license headers 2 years ago
netmon all: cleanup unused code, part 2 (#10670) 11 months ago
netns net/{interfaces,netmon}: remove "interesting", EqualFiltered API 1 year ago
netstat net/{netns,netstat}: use new x/sys/cpu.IsBigEndian 2 years ago
netutil all: cleanup unused code, part 2 (#10670) 11 months ago
packet all: cleanup unused code, part 1 (#10661) 11 months ago
ping net/ping: fix ICMP echo code field to 0 1 year ago
portmapper net/portmapper: check returned epoch from PMP and PCP protocols 11 months ago
proxymux all: cleanup unused code, part 1 (#10661) 11 months ago
routetable all: cleanup unused code, part 2 (#10670) 11 months ago
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tsdial all: cleanup unused code, part 1 (#10661) 11 months ago
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