Socket Statistics: Proposal for reading and displaying OS socket statistics for connections

Description:

Expose API for reading socket information for connections.

The intention is very similar to that of any tools like ss or netstat display. It would be useful to maintain this state as debugging becomes easier.

As an example, ss -4 state syn-recv would display all the tcp ipv4 network connections that are in the syn-recv state. With respect to TCP there are several states that a connection moves through, like listen, syn-sent, established, fin-wait1 etc. to name a few

Would it be useful to maintain the connection state?

This can also be extended to UDP sockets to see what state sockets are in unconn and estab

This could be information that envoy can render across all connections or for a specific connection.

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A specific use-case is addressed below, please read ahead if interested:

Usually it is possible to maintain count of total connections after the TCP three-way handshake. In cases where users are accessing the servers from geographies that have poor internet; there could be several reasons as to why a TCP connection might not be complete.

• The SYN could be dropped as a result of which the server never recognizes the intent of the client to connect.
• The SYN received is responded by a SYN-ACK by Envoy on the server to start establishing a connection(or completing the three-way handshake); however the SYN-ACK never reaches the client. This could happen due to many reasons like having mistaken routing table entries in the peering ISPs, degraded underlying network infrastructure etc.
• The motivation is for envoy running on a node to capture all half open TCP connections and relay it to a BI tool for analytics and resolving this problem
• Having half open connections directly translates to loss in business as this indicates a potential client trying to make a transaction but was unsuccessful due to the infrastructure.
• Furthermore, this client is not recorded in making an attempt to transact; thus the server could be permanently blind to these clients unless monitored.

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This could be a generic API that can be customized to specific OS (BSD/Linux, macOS, Windows etc) to provide other investigative statistics

[optional Relevant Links:]

https://linux.die.net/man/8/ss https://linux.die.net/man/8/netstat