[msutovsky-r7]

This adds support for migrate command on Mettle side for Linux x64/x86. This PR only adds support for Mettle to inject migrate stub and execute payload, session handling needs to be taken care in Framework. Currently, the migrate needs privilege to use ptrace syscall.

[Copilot]

Pull request overview

Adds Linux x64/x86 support for the migrate command in mettle by introducing a ptrace-based injector and exposing transport/socket details needed to stage the new session.

Changes:

• Adds new TLV fields and core TLV handlers for core_migrate and core_transport_list.
• Introduces a new ptrace-based injection implementation (base_inject.*) and wires it into the build.
• Adds APIs to retrieve the underlying socket FD from the active C2 transport.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 17 comments.

Show a summary per file

File	Description
mettle/src/tlv_types.h	Adds migrate-related TLVs and adjusts transport-group TLV ID.
mettle/src/network_client.h	Exposes network_client accessors for bufferev and socket FD.
mettle/src/network_client.c	Implements the new network_client accessor functions.
mettle/src/coreapi.c	Adds core_migrate and core_transport_list handlers and registers them.
mettle/src/c2_tcp.c	Adds c2_transport_get_socket_fd() implementation (currently TCP-specific).
mettle/src/c2.h	Exposes c2_get_next_transport() and c2_transport_get_socket_fd() prototypes.
mettle/src/c2.c	Implements c2_get_next_transport() (and introduces an extra c2_get_fd stub).
mettle/src/bufferev.h	Adds bufferev_get_socket_fd() declaration.
mettle/src/bufferev.c	Implements bufferev_get_socket_fd().
mettle/src/base_inject.h	Introduces injector header/API for migrate support.
mettle/src/base_inject.c	Adds ptrace-based injector implementation for Linux migrate.
mettle/src/Makefile.am	Adds base_inject.c to libmettle sources.

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[Copilot]

c2_transport_get_socket_fd() is assumed to work for the current transport, but mettle supports non-TCP transports (e.g. http/https). The current implementation of c2_transport_get_socket_fd() casts the transport ctx to tcp_ctx, which will be invalid for HTTP and can crash or leak memory. Either (a) move this API behind transport callbacks so each transport type can implement it safely, or (b) explicitly restrict migrate to fd/tcp transports and fail cleanly for others; also handle fd == -1 before calling migrate().

Suggested change

	if(migrate(pid, migrate_stub, stub_length, payload, payload_length, uuid, fd))
	/* Only attempt migration when we have a valid transport file descriptor. */
	if (fd >= 0 && migrate(pid, migrate_stub, stub_length, payload, payload_length, uuid, fd))