tree 8b366dada8f90a85a2423cbf3681d9e9db485a54
parent 952bce8575a5f0f0255e974d130c119cb4e712e5
author achernya <achernya@google.com> 1667674112 -0700
committer Copybara-Service <copybara-worker@google.com> 1667674145 -0700

IETF CONNECT-IP Hackathon: TUN device for masque_client

This change makes it possible for masque_client to bring up a TUN
device, rather than sending a single encapsulated request, if
--bring_up_tun is passed.

For now, the MTU is hard-coded to 1280, but with this, a connection to
testvm.masque.uno is able to bring up a tun0 that can hit https://www.google.com!

```
blaze build third_party/quic/masque/... && cp -f blaze-bin/third_party/quic/masque/masque_client /tmp && sudo /tmp/masque_client --disable_certificate_verification --masque_mode=connect-ip testvm.masque.uno:9661 --bring_up_tun --uid= --alsologtostderr
curl -D /dev/stdout -4 --interface tun0 "https://www.google.com"
```

PiperOrigin-RevId: 486375988