MINOR: vars/cli: add a "get var" CLI command to retrieve global variables

Process-wide variables can now be displayed from the CLI using "get var"
followed by the variable name. They must all start with "proc." otherwise
they will not be found. The output is very similar to the one of the
debug converter, with a type and value being reported for the embedded
sample.

This command is limited to clients with the level "operator" or higher,
since it can possibly expose traffic-related data.

doc/management.txt

@@ -1770,6 +1770,12 @@ get acl <acl> <value>
 
      type="<type>":         The type of the returned sample.
 
+get var <name>
+  Show the existence, type and contents of the process-wide variable 'name'.
+  Only process-wide variables are readable, so the name must begin with
+  'proc.' otherwise no variable will be found. This command requires levels
+  "operator" or "admin".
+
 get weight <backend>/<server>
   Report the current weight and the initial weight of server <server> in
   backend <backend> or an error if either doesn't exist. The initial weight is

reg-tests/sample_fetches/vars.vtc

@@ -26,6 +26,11 @@ haproxy h1 -conf {
 	http-request return status 200 hdr x-var "proc=%[var(proc.int5)] sess=%[var(sess.int5)] req=%[var(req.int5)] str=%[var(proc.str)] uuid=%[var(proc.uuid)]"
 } -start
 
+haproxy h1 -cli {
+    send "get var proc.int5"
+    expect ~ "^proc.int5: type=sint value=<5>$"
+}
+
 client c1 -connect ${h1_fe1_sock} {
     txreq -req GET -url /req1_1
     rxresp
@@ -38,6 +43,11 @@ client c1 -connect ${h1_fe1_sock} {
     expect resp.http.x-var ~ "proc=10 sess=20 req=10 str=this is a string uuid=[0-9a-f]*-[0-9a-f]*-[0-9a-f]*-[0-9a-f]*-[0-9a-f]*"
 } -run
 
+haproxy h1 -cli {
+    send "get var proc.int5"
+    expect ~ "^proc.int5: type=sint value=<10>$"
+}
+
 client c2 -connect ${h1_fe1_sock} {
     txreq -req GET -url /req2_1
     rxresp
@@ -49,3 +59,8 @@ client c2 -connect ${h1_fe1_sock} {
     expect resp.status == 200
     expect resp.http.x-var ~ "proc=20 sess=40 req=20 str=this is a string uuid=[0-9a-f]*-[0-9a-f]*-[0-9a-f]*-[0-9a-f]*-[0-9a-f]*"
 } -run
+
+haproxy h1 -cli {
+    send "get var proc.int5"
+    expect ~ "^proc.int5: type=sint value=<20>$"
+}

src/vars.c

@@ -2,8 +2,10 @@
 
 #include <haproxy/api.h>
 #include <haproxy/arg.h>
+#include <haproxy/buf.h>
 #include <haproxy/cfgparse.h>
 #include <haproxy/check.h>
+#include <haproxy/cli.h>
 #include <haproxy/global.h>
 #include <haproxy/http.h>
 #include <haproxy/http_rules.h>
@@ -867,6 +869,49 @@ static int vars_parse_global_set_var(char **args, int section_type, struct proxy
 	return ret;
 }
 
+/* parse CLI's "get var <name>" */
+static int vars_parse_cli_get_var(char **args, char *payload, struct appctx *appctx, void *private)
+{
+	struct vars *vars;
+	struct sample smp;
+	int i;
+
+	if (!cli_has_level(appctx, ACCESS_LVL_OPER))
+		return 1;
+
+	if (!*args[2])
+		return cli_err(appctx, "Missing process-wide variable identifier.\n");
+
+	vars = get_vars(NULL, NULL, SCOPE_PROC);
+	if (!vars || vars->scope != SCOPE_PROC)
+		return 0;
+
+	if (!vars_get_by_name(args[2], strlen(args[2]), &smp))
+		return cli_err(appctx, "Variable not found.\n");
+
+	/* the sample returned by vars_get_by_name() is allocated into a trash
+	 * chunk so we have no constraint to manipulate it.
+	 */
+	chunk_printf(&trash, "%s: type=%s value=", args[2], smp_to_type[smp.data.type]);
+
+	if (!sample_casts[smp.data.type][SMP_T_STR] ||
+	    !sample_casts[smp.data.type][SMP_T_STR](&smp)) {
+		chunk_appendf(&trash, "(undisplayable)");
+	} else {
+		/* Display the displayable chars*. */
+		b_putchr(&trash, '<');
+		for (i = 0; i < smp.data.u.str.data; i++) {
+			if (isprint((unsigned char)smp.data.u.str.area[i]))
+				b_putchr(&trash, smp.data.u.str.area[i]);
+			else
+				b_putchr(&trash, '.');
+		}
+		b_putchr(&trash, '>');
+		b_putchr(&trash, 0);
+	}
+	return cli_msg(appctx, LOG_INFO, trash.area);
+}
+
 static int vars_max_size(char **args, int section_type, struct proxy *curpx,
                          const struct proxy *defpx, const char *file, int line,
                          char **err, unsigned int *limit)
@@ -1016,3 +1061,11 @@ static struct cfg_kw_list cfg_kws = {{ },{
 }};
 
 INITCALL1(STG_REGISTER, cfg_register_keywords, &cfg_kws);
+
+
+/* register cli keywords */
+static struct cli_kw_list cli_kws = {{ },{
+	{ { "get",   "var", NULL }, "get var <name> : retrieve contents of a process-wide variable", vars_parse_cli_get_var, NULL },
+	{ { NULL }, NULL, NULL, NULL }
+}};
+INITCALL1(STG_REGISTER, cli_register_kw, &cli_kws);