88db09bafe net: handle multi-part netlink responses (willcl-ark)
42e99ad773 net: skip non-route netlink responses (willcl-ark)
57ce645f05 net: filter for default routes in netlink responses (willcl-ark)
Pull request description:
...for default route in pcp pinholing.
Currently we only make a single recv call, which trucates results from large routing tables, or in the case the kernel may split the message into multiple responses (which may happen with `NLM_F_DUMP`).
We also do not filter on the default route. For IPv6, this led to selecting the first route with an `RTA_GATEWAY` attribute, often a non-default route instead of the actual default. This caused PCP port mapping failures because the wrong gateway was used.
Fix both issues by adding multi-part handling of responses and filter for the default route.
Limit responses to ~ 1MB to prevent any router-based DoS.
ACKs for top commit:
achow101:
ACK 88db09bafe
davidgumberg:
Code Review re-ACK 88db09b
Sjors:
re-utACK 88db09bafe
Tree-SHA512: ea5948edebfad5896a487a61737aa5af99f529fad3cf3da68dced456266948238a7143383847e79a7bb90134e023eb173c25116d8eb80ff57fa4c4a0377ca1ed
Handle multi-part netlink responses to prevent truncated results from
large routing tables.
Previously, we only made a single recv call, which led to incomplete
results when the kernel split the message into multiple responses (which
happens frequently with NLM_F_DUMP).
Also guard against a potential hanging issue where the code would
indefinitely wait for NLMSG_DONE for non-multi-part responses by
detecting the NLM_F_MULTI flag and only continue waiting when necessary.
We really just want to skip this when building for Windows. So do that,
and remove the two header checks (we also already use both of these
headers, unguarded, in the !windows part of the codebase).
Squash the two *iffaddrs defines into one, as I haven't seen an
iffaddrs.h that implements one, but not the other.
Filter netlink responses to only consider default routes by checking the
destination prefix length (rtm_dst_len == 0).
Previously, we selected the first route with an RTA_GATEWAY attribute,
which for IPv6 often resulted in choosing a non-default route instead of
the actual default.
This caused occasional PCP port mapping failures because a gateway for a
non-default route was selected.
Instead of a `gethostname` hack, use the official way of calling
`GetAdaptersAddresses` to get local network addresses on Windows.
As additional cleanup, move out `FromSockAddr` from MacOS and use it
everywhere appropriate.
Suggested by Ava Chow.
In almost all cases (the only exception is `getifaddrs`), we know the
size of the data passed into SetSockAddr, so we can check this to be
what is expected.
