tests: add --gdb-use-emacs option

When specified `--gdb-use-emacs` will launch the daemon with gdb inside a
running emacs server using `emacsclient --eval` commands.

Signed-off-by: Christian Hopps <[email protected]>

doc/developer/topotests.rst

@@ -583,6 +583,12 @@ Here's an example of launching ``zebra`` and ``bgpd`` inside ``gdb`` on router
           --gdb-breakpoints=nb_config_diff \
           all-protocol-startup
 
+Finally, for Emacs users, you can specify ``--gdb-use-emacs``. When specified
+the first router and daemon to be launched in gdb will be launched and run with
+Emacs gdb functionality by using `emacsclient --eval` commands. This provides an
+IDE debugging experience for Emacs users. This functionality works best when
+using password-less sudo.
+
 Reporting Memleaks with FRR Memory Statistics
 """""""""""""""""""""""""""""""""""""""""""""
 

tests/topotests/conftest.py

@@ -102,6 +102,12 @@ def pytest_addoption(parser):
         help="Comma-separated list of routers to spawn gdb on, or 'all'",
     )
 
+    parser.addoption(
+        "--gdb-use-emacs",
+        action="store_true",
+        help="Use emacsclient to run gdb instead of a shell",
+    )
+
     parser.addoption(
         "--logd",
         action="append",

tests/topotests/lib/topotest.py

@@ -31,7 +31,7 @@
 import lib.topolog as topolog
 from lib.micronet_compat import Node
 from lib.topolog import logger
-from munet.base import Timeout
+from munet.base import commander, get_exec_path_host, Timeout
 
 from lib import micronet
 
@@ -1363,6 +1363,8 @@ def setup_node_tmpdir(logdir, name):
 class Router(Node):
     "A Node with IPv4/IPv6 forwarding enabled"
 
+    gdb_emacs_router = None
+
     def __init__(self, name, *posargs, **params):
         # Backward compatibility:
         #   Load configuration defaults like topogen.
@@ -1799,6 +1801,7 @@ def startRouterDaemons(self, daemons=None, tgen=None):
         gdb_breakpoints = g_pytest_config.get_option_list("--gdb-breakpoints")
         gdb_daemons = g_pytest_config.get_option_list("--gdb-daemons")
         gdb_routers = g_pytest_config.get_option_list("--gdb-routers")
+        gdb_use_emacs = bool(g_pytest_config.option.gdb_use_emacs)
         valgrind_extra = bool(g_pytest_config.option.valgrind_extra)
         valgrind_memleaks = bool(g_pytest_config.option.valgrind_memleaks)
         strace_daemons = g_pytest_config.get_option_list("--strace-daemons")
@@ -1925,13 +1928,19 @@ def start_daemon(daemon, extra_opts=None):
             if extra_opts:
                 cmdopt += " " + extra_opts
 
-            if (
-                (gdb_routers or gdb_daemons)
+            if ((not gdb_use_emacs or Router.gdb_emacs_router)
+                and (gdb_routers or gdb_daemons)
                 and (
                     not gdb_routers or self.name in gdb_routers or "all" in gdb_routers
                 )
                 and (not gdb_daemons or daemon in gdb_daemons or "all" in gdb_daemons)
             ):
+                if Router.gdb_emacs_router is not None:
+                    logger.warning(
+                        "--gdb-use-emacs can only run a single router and daemon, using"
+                        " new window"
+                    )
+
                 if daemon == "snmpd":
                     cmdopt += " -f "
 
@@ -1942,9 +1951,61 @@ def start_daemon(daemon, extra_opts=None):
                 for bp in gdb_breakpoints:
                     gdbcmd += " -ex 'b {}'".format(bp)
                 gdbcmd += " -ex 'run {}'".format(cmdopt)
-
                 self.run_in_window(gdbcmd, daemon)
 
+                logger.info(
+                    "%s: %s %s launched in gdb window", self, self.routertype, daemon
+                )
+            elif (gdb_use_emacs
+                  and (daemon in gdb_daemons)
+                  and (not gdb_routers or self.name in gdb_routers)
+                  ):
+                assert Router.gdb_emacs_router is None
+                Router.gdb_emacs_router = self
+
+                if daemon == "snmpd":
+                    cmdopt += " -f "
+                cmdopt += rediropt
+
+                sudo_path = get_exec_path_host("sudo")
+                ecbin = [
+                    sudo_path,
+                    "-Eu",
+                    os.environ["SUDO_USER"],
+                    get_exec_path_host("emacsclient")
+                ]
+                pre_cmd = self._get_pre_cmd(True, False, ns_only=True, root_level=True)
+                gdbcmd = f"{sudo_path} {pre_cmd} gdb -i=mi {binary}"
+
+                commander.cmd_raises(ecbin + ["--eval", f'(gdb "{gdbcmd}"))',])
+
+                # TODO: figure out a better way to determine when gdb is ready in emacs
+                time.sleep(10)
+
+                # target gdb commands
+                cmd = 'set breakpoint pending on'
+                self.cmd_raises(
+                    ecbin + [
+                        "--eval",
+                        f'(gud-gdb-run-command-fetch-lines "{cmd}" "*gud-gdb*")',
+                    ]
+                )
+                # gdb breakpoints
+                for bp in gdb_breakpoints:
+                    self.cmd_raises(
+                        ecbin + [
+                            "--eval",
+                            f'(gud-gdb-run-command-fetch-lines "br {bp}" "*gud-gdb*")',
+                        ]
+                    )
+                # gdb run cmd
+                self.cmd_raises(
+                    ecbin + [
+                        "--eval",
+                        f'(gud-gdb-run-command-fetch-lines "run {cmdopt}" "*gud-gdb*")',
+                    ]
+                )
+
                 logger.info(
                     "%s: %s %s launched in gdb window", self, self.routertype, daemon
                 )