Quote VSL fields that are known to contain spaces

The test case covers the last field of Backend_health records.

bin/varnishd/cache/cache_acceptor.c

@@ -508,7 +508,7 @@ vca_accept_task(struct worker *wrk, void *arg)
 				    lport, VTCP_PORTBUFSIZE);
 			}
 
-			VSL(SLT_SessError, 0, "%s %s %s %d %d %s",
+			VSL(SLT_SessError, 0, "%s %s %s %d %d \"%s\"",
 			    wa.acceptlsock->name, laddr, lport,
 			    ls->sock, i, vstrerror(i));
 			(void)Pool_TrySumstat(wrk);

bin/varnishd/cache/cache_backend_probe.c

@@ -181,7 +181,7 @@ VBP_Update_Backend(struct vbp_target *vt)
 	vt->backend->sick = i;
 
 	AN(dir->vcl_name);
-	VSL(SLT_Backend_health, 0, "%s %s %s %s %u %u %u %.6f %.6f %s",
+	VSL(SLT_Backend_health, 0, "%s %s %s %s %u %u %u %.6f %.6f \"%s\"",
 	    dir->vcl_name, chg ? "Went" : "Still",
 	    i ? "sick" : "healthy", bits,
 	    vt->good, vt->threshold, vt->window,

bin/varnishtest/tests/r02872.vtc

 varnishtest "VSL quoted fields"
 
+server s1 {
+        rxreq
+        txresp
+} -start
+
 varnish v1 -vcl {
 	import std;
-        backend be none;
+        backend be {
+                .host = "${s1_sock}";
+                .probe = { .interval = 1m; }
+        }
 	sub vcl_recv {
 		# a series of 3-fields log records
 		std.log({"  custom   log     "ok" "});
@@ -24,3 +32,10 @@ client c1 {
 shell -expect "2" {
         varnishlog -d -n ${v1_name} -g raw -q 'VCL_Log[3]' | wc -l
 }
+
+server s1 -wait
+
+shell -expect "Went healthy" {
+        varnishlog -d -n ${v1_name} -g raw \
+		-q 'Backend_health[10] eq "HTTP/1.1 200 OK"'
+}

include/tbl/vsl_tags.h

@@ -191,7 +191,7 @@ SLTM(Length, 0, "Size of object body",
 
 SLTM(FetchError, 0, "Error while fetching object",
 	"Logs the error message of a failed fetch operation.\n\n"
-	"Error messages should be self-explanatory, yet the http connection"
+	"Error messages should be self-explanatory, yet the http connection\n"
 	"(HTC) class of errors is reported with these symbols:\n\n"
 	"\t* junk (-5): Received unexpected data\n"
 	"\t* close (-4): Connection closed\n"
@@ -272,11 +272,11 @@ SLTM(TTL, 0, "TTL set on object",
 SLTM(Fetch_Body, 0, "Body fetched from backend",
 	"Ready to fetch body from backend.\n\n"
 	"The format is::\n\n"
-	"\t%d (%s) %s\n"
+	"\t%d %s %s\n"
 	"\t|  |  |\n"
 	"\t|  |  +---- 'stream' or '-'\n"
-	"\t|   +--------- Text description of body fetch mode\n"
-	"\t+------------- Body fetch mode\n"
+	"\t|  +------- Text description of body fetch mode\n"
+	"\t+---------- Body fetch mode\n"
 	"\n"
 )