Node discovery periodically revalidates the nodes in its table by sending PING, checking
if they are still alive. I recently noticed some issues with the implementation of this
process, which can cause strange results such as nodes dropping unexpectedly, certain
nodes not getting revalidated often enough, and bad results being returned to incoming
FINDNODE queries.
In this change, the revalidation process is improved with the following logic:
- We maintain two 'revalidation lists' containing the table nodes, named 'fast' and 'slow'.
- The process chooses random nodes from each list on a randomized interval, the interval being
faster for the 'fast' list, and performs revalidation for the chosen node.
- Whenever a node is newly inserted into the table, it goes into the 'fast' list.
Once validation passes, it transfers to the 'slow' list. If a request fails, or the
node changes endpoint, it transfers back into 'fast'.
- livenessChecks is incremented by one for successful checks. Unlike the old implementation,
we will not drop the node on the first failing check. We instead quickly decay the
livenessChecks give it another chance.
- Order of nodes in bucket doesn't matter anymore.
I am also adding a debug API endpoint to dump the node table content.
Co-authored-by: Martin HS <martin@swende.se>
In all other UDPv4 methods, the deadline is checked first. It seems weird to me that ping is an exception. Deadline comparison is also less resource intensive.
Co-authored-by: Exca-DK <Exca-DK@users.noreply.github.com>
* p2p/discover: remove ReadRandomNodes
Even though it's public, this method is not callable by code outside of
package p2p/discover because one can't get a valid instance of Table.
* p2p/discover: add Table.Nodes
* p2p/discover: make Table settings configurable
In unit tests and externally developed cmd/devp2p test runs, it can be
useful to tune the timer intervals used by Table.
This changes the definitions of Ping and Pong, adding an optional field
for the sequence number. This field was previously encoded/decoded using
the "tail" struct tag, but using "optional" is much nicer.
This change improves discovery behavior in small networks. Very small
networks would often fail to bootstrap because all member nodes were
dropping table content due to findnode failure. The check is now changed
to avoid dropping nodes on findnode failure when their bucket is almost
empty. It also relaxes the liveness check requirement for FINDNODE/v4
response nodes, returning unverified nodes as results when there aren't
any verified nodes yet.
The "findnode failed" log now reports whether the node was dropped
instead of the number of results. The value of the "results" was
always zero by definition.
Co-authored-by: Felix Lange <fjl@twurst.com>
* p2p: add low port check in dialer
We already have a check like this for UDP ports, add a similar one in
the dialer. This prevents dials to port zero and it's also an extra
layer of protection against spamming HTTP servers.
* p2p/discover: use errLowPort in v4 code
* p2p: change port check
* p2p: add comment
* p2p/simulations/adapters: ensure assigned port is in all node records
This adds an implementation of the current discovery v5 spec.
There is full integration with cmd/devp2p and enode.Iterator in this
version. In theory we could enable the new protocol as a replacement of
discovery v4 at any time. In practice, there will likely be a few more
changes to the spec and implementation before this can happen.
* p2p/discover: export Ping and RequestENR
These two are useful for checking the status of a node.
* cmd/devp2p: add devp2p debug tool
This is a new tool for debugging p2p issues. It supports a few
basic tasks for now, but many more things can and will be added
in the near future.
devp2p enrdump -- prints ENRs readably
devp2p discv4 ping -- checks if a node is up
devp2p discv4 requestenr -- gets a node's record
devp2p discv4 resolve -- finds a node through the DHT
This change implements EIP-868. The UDPv4 transport announces support
for the extension in ping/pong and handles enrRequest messages.
There are two uses of the extension: If a remote node announces support
for EIP-868 in their pong, node revalidation pulls the node's record.
The Resolve method requests the record unconditionally.
This change restructures the internals of p2p/discover to make room for
the discv5 code which will soon be added to this package.
- packet type names now have a "V4" suffix.
- ListenUDP returns *UDPv4 instead of *Table. This technically breaks
the API but the only caller in go-ethereum is package p2p, which uses
a compatible interface and doesn't need changes.
- The internal transport interface is changed to make Table reusable for v5.
- The 'lookup' code moves from table to transport. This required
updating the lookup unit test to use udpTest instead of a custom transport.
Felix Lange
Undefinedor
yzb
lightclient
Exca-DK
Justin Traglia
Seungbae.yu
Håvard Anda Estensen
baptiste-b-pegasys
timcooijmans
Péter Szilágyi
Felix Lange
Martin Holst Swende