Commits on Oct 14, 2021

1. addrmgr: make safe accessors for addresses …

   The KnownAddress returned by GetAddress is not safely usable while the
   AddrManager is in use by another goroutine since the fields of
   the KnownAddress are mutable. Although AddrManager treats a
   *wire.NetAddress as immutable, the KnownAddress.na field itself
   is reassigned. Similarly, the lastattempt field is mutable.
   
   To address this API usability issue, this commit makes two new accessor
   methods:
   
   - GetNetAddress returns the *wire.NetAddress and the lastAttempt
   - GetAddressCopy returns a copy of the *KnownAddress
   
   The original GetAddress remains because it is designed to reference
   the KnownAddress that is still in the AddrManager, allowing operations
   by the AddrManager such as connects and attempts to be reflected in the
   initially returned KnownAddress. The blackbox addrmgr tests are
   are designed around this behavior.
   
   However, it is not safe to use GetAddress from another goroutine such
   as the connmgr's GetNewAddress function (newAddressFunc closure defined
   in newServer) concurrent with updates to the KnownAddress such as via
   (*Peer).inHandler, which has callbacks to the AddrManager that may
   mutate the KnownAddress.
   
   An alternate resolution would involve adding a Mutex to a KnownAddress,
   but this would be a more substantial change, which would likely create
   unnecessary lock contention and complexity. Returning copies is safer
   and simpler.

   

   chappjc committed Oct 14, 2021
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