[PATCH nvme-cli rfc] fabrics: support default connect/discover args

[sagi@grimberg.me (Sagi Grimberg)]

Introduce /etc/nvme/defargs.conf where we allow the user to
specify connect/discover parameters once and not for every
controller. The cli will always ingest the content of this
file before parsing cmdline args such that the user can
override them.

The format is simply writing the arguments into the file as
if they were appended to the execution command.

Also, properly install this file with some minimal documentation.

Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
This was raised before in the past that we don't have some place
to store default connect args.

For example, when handling automatic discovery change log events
this can be a way for the user to set global default arguments.

Feedback is welcome.

 Makefile            |  3 +++
 etc/defargs.conf.in |  5 ++++
 fabrics.c           | 63 +++++++++++++++++++++++++++++++++++++++++++++
 nvme.spec.in        |  1 +
 4 files changed, 72 insertions(+)
 create mode 100644 etc/defargs.conf.in

diff --git a/Makefile b/Makefile
index 4bfbebbd156a..6f11941b5d3e 100644
--- a/Makefile
+++ b/Makefile
@@ -105,6 +105,9 @@ install-etc:
 	if [ ! -f $(DESTDIR)$(SBINDIR)/nvme/discovery.conf ]; then \
 		$(INSTALL) -m 644 -T ./etc/discovery.conf.in $(DESTDIR)$(SYSCONFDIR)/nvme/discovery.conf; \
 	fi
+	if [ ! -f $(DESTDIR)$(SBINDIR)/nvme/defargs.conf ]; then \
+		$(INSTALL) -m 644 -T ./etc/defargs.conf.in $(DESTDIR)$(SYSCONFDIR)/nvme/defargs.conf; \
+	fi
 
 install-spec: install-bin install-man install-bash-completion install-zsh-completion install-etc
 install: install-spec install-hostparams
diff --git a/etc/defargs.conf.in b/etc/defargs.conf.in
new file mode 100644
index 000000000000..e91106bf5bbf
--- /dev/null
+++ b/etc/defargs.conf.in
@@ -0,0 +1,5 @@
+# Used for extracting default controller connect parameters
+#
+# Example:
+# --keep-alive-tmo=<x> --reconnect-delay=<y> --ctrl-loss-tmo=<z> --nr-io-queues=<u>
+# --queue-size=<v>
diff --git a/fabrics.c b/fabrics.c
index 511de06aec97..e609e679c832 100644
--- a/fabrics.c
+++ b/fabrics.c
@@ -72,8 +72,10 @@ static struct config {
 #define PATH_NVMF_DISC		"/etc/nvme/discovery.conf"
 #define PATH_NVMF_HOSTNQN	"/etc/nvme/hostnqn"
 #define PATH_NVMF_HOSTID	"/etc/nvme/hostid"
+#define PATH_NVMF_DEFARGS	"/etc/nvme/defargs.conf"
 #define SYS_NVME		"/sys/class/nvme"
 #define MAX_DISC_ARGS		10
+#define MAX_DEF_ARGS		10
 #define MAX_DISC_RETRIES	10
 
 enum {
@@ -894,6 +896,59 @@ static int do_discover(char *argstr, bool connect)
 	return ret;
 }
 
+static int nvmf_parse_defargs(const char *desc,
+		const struct argconfig_commandline_options *opts)
+{
+	FILE *f;
+	char line[256], *ptr, *args, **argv;
+	int argc = 0, ret = 0;
+
+	f = fopen(PATH_NVMF_DEFARGS, "r");
+	if (f == NULL)
+		return 0;
+
+	while (fgets(line, sizeof(line), f) != NULL) {
+		if (line[0] == '#' || line[0] == '\n')
+			continue;
+
+		args = strdup(line);
+		if (!args) {
+			fprintf(stderr, "failed to strdup args\n");
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		argv = calloc(MAX_DEF_ARGS, BUF_SIZE);
+		if (!argv) {
+			fprintf(stderr, "failed to allocate argv vector\n");
+			free(args);
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		argc = 0;
+		argv[argc++] = "dummy";
+		while ((ptr = strsep(&args, " =\n")) != NULL)
+			argv[argc++] = ptr;
+
+		ret = argconfig_parse(argc, argv, desc, opts, &cfg, sizeof(cfg));
+		free(args);
+		free(argv);
+		if (ret)
+			goto out;
+
+		if (cfg.transport || cfg.traddr || cfg.trsvcid || cfg.nqn) {
+			fprintf(stderr, "args transport, traddr, trsvcid, nqn "
+				"cannot have a default\n");
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+out:
+	fclose(f);
+	return ret;
+}
+
 static int discover_from_conf_file(const char *desc, char *argstr,
 		const struct argconfig_commandline_options *opts, bool connect)
 {
@@ -981,6 +1036,10 @@ int discover(const char *desc, int argc, char **argv, bool connect)
 		{NULL},
 	};
 
+	ret = nvmf_parse_defargs(desc, command_line_options);
+	if (ret)
+		return ret;
+
 	ret = argconfig_parse(argc, argv, desc, command_line_options, &cfg,
 			sizeof(cfg));
 	if (ret)
@@ -1026,6 +1085,10 @@ int connect(const char *desc, int argc, char **argv)
 		{NULL},
 	};
 
+	ret = nvmf_parse_defargs(desc, command_line_options);
+	if (ret)
+		return ret;
+
 	ret = argconfig_parse(argc, argv, desc, command_line_options, &cfg,
 			sizeof(cfg));
 	if (ret)
diff --git a/nvme.spec.in b/nvme.spec.in
index 6934f8fd605b..e2240b61d79e 100644
--- a/nvme.spec.in
+++ b/nvme.spec.in
@@ -35,6 +35,7 @@ make install-spec DESTDIR=%{buildroot} PREFIX=/usr
 %{_sysconfdir}/nvme/hostnqn
 %{_sysconfdir}/nvme/hostid
 %{_sysconfdir}/nvme/discovery.conf
+%{_sysconfdir}/nvme/defargs.conf
 
 %clean
 rm -rf $RPM_BUILD_ROOT
-- 
2.17.1