* Allow custom local address resolvers.
#27881 introduces the concept of EDS clusters with hosts that have multiple (potentially > 2) IP addresses.
The current implementation of UpstreamLocalAddressSelector limits the number of source addresses in BindConfig artificially to 2, and further requires that the addresses be of different address families.
The workaround for this (if we need to specify more than 2 source addresses or have multiple addresses from the same family) is to use a custom address resolver that resolves the bind config address to nullptr (and therefore ignore it) and call bind in a customised SocketInterfaceImpl to a local source address determined by the SocketInterfaceImpl specialisation.
This PR makes it possible to define a custom local address selector, that makes it easy to work with a custom address resolver to pick the right source address based on the upstream address selected by HappyEyeballsConnectionImpl
Signed-off-by: pcrao <pcrao@google.com>
Mirrored from https://github.com/envoyproxy/envoy @ da47a54a8ccbaa384c4cb62a5f4fcd4745a72c37
update-envoy[bot]
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