tests: Use show module to get bgp's pid

[donaldsharp]

The topotest is using pidof bgpd which is ok
when you run a test by itself, but when you
are running the topotests in parallel, this
is a bit of a problem. Fix.

[greptile-apps]

Greptile Summary

This PR replaces pidof bgpd (a host-wide process search) with a new _daemon_pid() helper that queries show module via vtysh on the specific router object, scoping the PID lookup to the correct network namespace when tests run in parallel.

• Introduces _daemon_pid(router, daemon) that parses the per-daemon \"Module information for <name>:\" sections from show module output to extract the running PID.
• Replaces three call sites of router.net.cmd(\"pidof bgpd\").strip() with _daemon_pid(r1, \"bgpd\"), fixing false PID matches that could occur when multiple test instances run bgpd simultaneously.

Confidence Score: 4/5

Safe to merge — the change correctly scopes PID lookups to the individual router namespace, and the regex parsing matches the actual show modules output format in FRR.

The fix is logically sound and addresses a real parallel-test isolation problem. The only minor concern is using the abbreviated command show module instead of the full show modules string, which works today via FRR abbreviation matching but is slightly less explicit.

No files require special attention beyond the minor command-name abbreviation in _daemon_pid.

Important Files Changed

Filename	Overview
tests/topotests/bgp_bmp/test_bgp_bmp_mirror.py	Adds _daemon_pid() helper using vtysh_cmd("show module") to replace the host-global pidof bgpd; the command string is the abbreviated form of the registered show modules command.

Sequence Diagram

sequenceDiagram
    participant Test as test_bgp_bmp_mirror
    participant Helper as _daemon_pid()
    participant Router as router (vtysh)
    participant bgpd

    Note over Test: Before fix - host-wide
    Test->>Router: net.cmd("pidof bgpd")
    Router-->>Test: any bgpd PID on host

    Note over Test: After fix - router-scoped
    Test->>Helper: _daemon_pid(router, "bgpd")
    Helper->>Router: vtysh_cmd("show module")
    Router->>bgpd: show modules
    bgpd-->>Router: Module information for bgpd, pid: 1234
    Router-->>Helper: output text
    Helper-->>Test: 1234 (bgpd PID in this namespace)

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Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
tests/topotests/bgp_bmp/test_bgp_bmp_mirror.py:100
The vtysh command registered in `lib/lib_vty.c` and `vtysh/vtysh.c` is `"show modules"` (with a trailing `s`). FRR's CLI supports unambiguous abbreviations, so `"show module"` works today, but using the full command name avoids any future ambiguity if another `show module*` command is ever added.

```suggestion
    output = router.vtysh_cmd("show modules")
```

_{Reviews (1): Last reviewed commit: "tests: Use `show module` to get bgp's pi..." | Re-trigger Greptile}

[greptile-apps]

The vtysh command registered in lib/lib_vty.c and vtysh/vtysh.c is "show modules" (with a trailing s). FRR's CLI supports unambiguous abbreviations, so "show module" works today, but using the full command name avoids any future ambiguity if another show module* command is ever added.

Suggested change

	output = router.vtysh_cmd("show module")
	output = router.vtysh_cmd("show modules")

Prompt To Fix With AI

This is a comment left during a code review.
Path: tests/topotests/bgp_bmp/test_bgp_bmp_mirror.py
Line: 100

Comment:
The vtysh command registered in `lib/lib_vty.c` and `vtysh/vtysh.c` is `"show modules"` (with a trailing `s`). FRR's CLI supports unambiguous abbreviations, so `"show module"` works today, but using the full command name avoids any future ambiguity if another `show module*` command is ever added.

```suggestion
    output = router.vtysh_cmd("show modules")
```

How can I resolve this? If you propose a fix, please make it concise.