Only retry UDP socket bind if it returned EADDRINUSE #1761
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Currently, the NextRandomUdpSocket picks a random port in the ephemeral port range and attempts to bind a UDP socket to it. If that bind operation fails, it indiscriminately retries several times before allowing the caller to poll again, assuming that it failed because the randomly selected port was in use. However, this means that if `bind` fails for another reason than the requested port being unavailable, such as insufficient capabilities to bind a socket, this error will not be propagated to the caller. Instead, with this change, NextRandomUdpSocket immediately returns any error returned from `bind` unless it is EADDRINUSE, in which case, it picks another random port and tries again as before.
bluejekyll
approved these changes
Aug 8, 2022
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Currently, the NextRandomUdpSocket picks a random port in the ephemeral
port range and attempts to bind a UDP socket to it. If that bind
operation fails, it indiscriminately retries several times before
allowing the caller to poll again, assuming that it failed because the
randomly selected port was in use.
However, this means that if
bindfails for another reason than therequested port being unavailable, such as insufficient capabilities to
bind a socket, this error will not be propagated to the caller. Instead,
with this change, NextRandomUdpSocket immediately returns any error
returned from
bindunless it is EADDRINUSE, in which case, it picksanother random port and tries again as before.
This was observed in a test on Fuchsia because, if the DNS resolver does not
have access to the capability required from the network stack to create and bind
sockets, it will see an
EPIPE(broken pipe) error onbind.