In cases of very large reorganisations (hundreds of blocks), a situation
may appear where an 'inv' is sent as response to a 'getblocks', but the
last block mentioned in the inv is already known to the receiver node.
However, the supplying node uses a request for this last block as a
trigger to send the rest of the inv blocks. If it never comes, the block
chain download is stuck.
This commit makes the receiver node always request the last inv'ed block,
even if it is already known, to prevent this problem.
Sometimes a new block arrives in a new chain that was already the
best valid one, but wasn't marked that way. This happens for example
when network rules change to recover after a fork.
In this case, it is not necessary to do the entire reorganisation
inside a single db commit. These can become huge, and exceed the
objects/lockers limits in bdb. This patch limits the blocks the
actual reorganisation is applied to, and adds the next blocks
afterwards in separate db transactions.
Introduce the following network rule:
* a block is not valid if it contains a transaction whose hash
already exists in the block chain, unless all that transaction's
outputs were already spent before said block.
Warning: this is effectively a network rule change, with potential
risk for forking the block chain. Leaving this unfixed carries the
same risk however, for attackers that can cause a reorganisation
in part of the network.
Thanks to Russell O'Connor and Ben Reeves.
Doing so would allow an attack on old nodes, which would relay a
standard transaction spending a BIP16 output in an invalid way,
until reaching a new node, which will disconnect their peer.
Reported by makomk on IRC.
Design goals:
* Only keep a limited number of addresses around, so that addr.dat does not grow without bound.
* Keep the address tables in-memory, and occasionally write the table to addr.dat.
* Make sure no (localized) attacker can fill the entire table with his nodes/addresses.
See comments in addrman.h for more detailed information.
This also avoids flushing setAddrKnown until 24 hours has passed,
and avoids contacting the external IP services when not listening.
Advertising non-listening nodes is just addr message spam.
It doesn't help the network, in fact it hurts the network,
and it also hurts user's privacy.
Advertising far out of sync nodes doesn't help the network—
they can't even forward (most) transactions and wastes nodes
outbound slots.
Allow mining of min-difficulty blocks if 20 minutes have gone by without mining a regular-difficulty block.
Normal rules apply every 2016 blocks, though, so there may be a very-slow-to-confirm block at the difficulty-adjustment blocks.
This also removes an un-needed sigops-per-byte check when accepting transactions to the memory pool (un-needed assuming only standard transactions are being accepted). And it only counts P2SH sigops after the switchover date.
This introduces CNetAddr and CService, respectively wrapping an
(IPv6) IP address and an IP+port combination. This functionality used
to be part of CAddress, which also contains network flags and
connection attempt information. These extra fields are however not
always necessary.
These classes, along with logic for creating connections and doing
name lookups, are moved to netbase.{h,cpp}, which does not depend on
headers.h.
Furthermore, CNetAddr is mostly IPv6-ready, though IPv6
functionality is not yet enabled for the application itself.
so it takes a flag for how to interpret OP_EVAL.
Also increased IsStandard size of scriptSigs to 500 bytes, so
a 3-of-3 multisig transaction IsStandard.
OP_EVAL is a new opcode that evaluates an item on the stack as a script.
It enables a new type of bitcoin address that needs an arbitrarily
complex script to redeem.
Gavin Andresen