Hi!

Following up onthis discussion in UEFIRC, a downstream consumer ofuefi-rs in which I implemented a UEFI TCP client, this PR ports this TCP protocol modelling / client implementation touefi-rs proper.

I made a basic effort to triage some things that were directly modelled with no accoutrements intouefi-raw, but I'm sure more can be moved here. It would be nice to place types such asTCPv4Protocol inuefi-raw, but this currently contains 'client business logic' and therefore is placed inuefi.

Here are some samples on how the client introduced in this PR can be used to communicate over TCP:

• Initialize UEFI TCP stack and connect
• Receive data (this API can certainly be improved)
• Transmit data

Notes

• I believe theTCPv4* types introduced by this PR should be renamed toTcpv4 orTcp4 for consistency across the project?
• Ip4RouteTable (and theIp4IcmpType,Ip4ModeData, andIp4ConfigData types introduced by this PR) should perhaps be renamed toIpv4* for consistency withIpv4Address.
• I made a fair bit of effort during the development of this code to squash memory leaks, UAFs, and other shenanigans. However, I am not absolutely certain that no issues exist. The code works fine for my use case (mostly receiving, occasional transmitting) and I have not noticed memory leaks.
• The client implementation is incomplete. For example, I have not bothered to implement acting as a TCP server.
• The client code currently contains some 'business logic' that may not be desirable to include inuefi-rs, or may not be desirable to include as-is. For example, the client currently internally waits up to 10 seconds for a DHCP-assigned IP. You might wish to just include the protocol definitions inuefi-raw and omit all the business logic, which would be fine and makes sense.

Thank you for taking the time to get this PR ready for upstream inclusion!

Steps to Undraft

• Restart the work (PR is stale for almost 1.5 years now)

Checklist

• [☑️] Sensible git history (for example, squash "typo" or "fix" commits). See theRewriting History guide for help.
• [☑️] Update the changelog (if necessary)