Previously, Add() would return true if the function created a new
AddressInfo object, even if that object could not be successfully
entered into the new table and was deleted. That would happen if the new
table position was already taken and the existing entry could not be
removed.
Instead, return true if the new AddressInfo object is successfully
entered into the new table. This fixes a bug in the "Added %i addresses"
log, which would not always accurately log how many addresses had been
added.
p2p_addrv2_relay.py and p2p_addr_relay.py need to be updated since they
were incorrectly asserting on the buggy log (assuming that addresses are
added to addrman, when there could in fact be new table position
collisions that prevent some of those address records from being added).
While limitations on the influence of attackers on addrman already
exist (affected buckets are restricted to a subset based on incoming
IP / network group), there is no reason to permit them to let them
feed us addresses at more than a multiple of the normal network
rate.
This commit introduces a "token bucket" rate limiter for the
processing of addresses in incoming ADDR and ADDRV2 messages.
Every connection gets an associated token bucket. Processing an
address in an ADDR or ADDRV2 message from non-whitelisted peers
consumes a token from the bucket. If the bucket is empty, the
address is ignored (it is not forwarded or processed). The token
counter increases at a rate of 0.1 tokens per second, and will
accrue up to a maximum of 1000 tokens (the maximum we accept in a
single ADDR or ADDRV2). When a GETADDR is sent to a peer, it
immediately gets 1000 additional tokens, as we actively desire many
addresses from such peers (this may temporarily cause the token
count to exceed 1000).
The rate limit of 0.1 addr/s was chosen based on observation of
honest nodes on the network. Activity in general from most nodes
is either 0, or up to a maximum around 0.025 addr/s for recent
Bitcoin Core nodes. A few (self-identified, through subver) crawler
nodes occasionally exceed 0.1 addr/s.
Introduce a new message `sendaddrv2` to signal support for ADDRv2.
Send the new message immediately after sending the `VERACK` message.
Add support for receiving and parsing ADDRv2 messages.
Send ADDRv2 messages (instead of ADDR) to a peer if he has
advertised support for it.
Co-authored-by: Carl Dong <contact@carldong.me>
John Newbery