lib, log: Add log prefix length to internal logging protocol

This way log process knows which part of the text is the log prefix, and
which part is the logged text.

src/lib/failures.c

@@ -18,6 +18,7 @@
 #include <time.h>
 #include <poll.h>
 
+#define LOG_TYPE_FLAG_PREFIX_LEN 0x40
 #define LOG_TYPE_FLAG_DISABLE_LOG_PREFIX 0x80
 
 const char *failure_log_type_prefixes[LOG_TYPE_COUNT] = {
@@ -765,12 +766,12 @@ static int internal_send_split(string_t *full_str, size_t prefix_len)
 
 
 static bool line_parse_prefix(const char *line, enum log_type *log_type_r,
-			      bool *replace_prefix_r)
+			      bool *replace_prefix_r, bool *have_prefix_len_r)
 {
 	if (*line != 1)
 		return FALSE;
 
-	unsigned char log_type = (line[1] & 0x7f);
+	unsigned char log_type = (line[1] & 0x3f);
 	if (log_type == '\0') {
 		i_warning("Broken log line follows (type=NUL)");
 		return FALSE;
@@ -783,15 +784,18 @@ static bool line_parse_prefix(const char *line, enum log_type *log_type_r,
 	}
 	*log_type_r = log_type;
 	*replace_prefix_r = (line[1] & LOG_TYPE_FLAG_DISABLE_LOG_PREFIX) != 0;
+	*have_prefix_len_r = (line[1] & LOG_TYPE_FLAG_PREFIX_LEN) != 0;
 	return TRUE;
 }
 
 void i_failure_parse_line(const char *line, struct failure_line *failure)
 {
+	bool have_prefix_len = FALSE;
 
 	i_zero(failure);
 	if (!line_parse_prefix(line, &failure->log_type,
-			       &failure->disable_log_prefix)) {
+			       &failure->disable_log_prefix,
+			       &have_prefix_len)) {
 		failure->log_type = LOG_TYPE_ERROR;
 		failure->text = line;
 		return;
@@ -808,7 +812,21 @@ void i_failure_parse_line(const char *line, struct failure_line *failure)
 		failure->pid = 0;
 		return;
 	}
-	failure->text = line + 1;
+	line++;
+
+	if (have_prefix_len) {
+		if (str_parse_uint(line, &failure->log_prefix_len, &line) < 0 ||
+		    line[0] != ' ') {
+			/* unexpected, but ignore */
+		} else {
+			line++;
+			if (failure->log_prefix_len > strlen(line)) {
+				/* invalid */
+				failure->log_prefix_len = 0;
+			}
+		}
+	}
+	failure->text = line;
 }
 
 static void ATTR_NORETURN ATTR_FORMAT(2, 0)

src/lib/failures.h

@@ -29,6 +29,10 @@ enum log_type {
 struct failure_line {
 	pid_t pid;
 	enum log_type log_type;
+	/* If non-zero, the first log_prefix_len bytes in text indicate
+	   the log prefix. This implies disable_log_prefix=TRUE. */
+	unsigned int log_prefix_len;
+	/* Disable the global log prefix. */
 	bool disable_log_prefix;
 	const char *text;
 };

src/log/log-connection.c

@@ -243,7 +243,7 @@ log_it(struct log_connection *log, const char *line,
 	struct failure_line failure;
 	struct failure_context failure_ctx;
 	struct log_client *client = NULL;
-	const char *prefix;
+	const char *prefix = "";
 
 	if (log->master) {
 		log_parse_master_line(line, log_time, tm);
@@ -274,11 +274,16 @@ log_it(struct log_connection *log, const char *line,
 	failure_ctx.type = failure.log_type;
 	failure_ctx.timestamp = tm;
 	failure_ctx.timestamp_usecs = log_time->tv_usec;
-	if (failure.disable_log_prefix)
+	if (failure.log_prefix_len != 0) {
+		failure_ctx.log_prefix =
+			t_strndup(failure.text, failure.log_prefix_len);
+		failure.text += failure.log_prefix_len;
+	} else if (failure.disable_log_prefix) {
 		failure_ctx.log_prefix = "";
-
-	prefix = client != NULL && client->prefix != NULL ?
-		client->prefix : log->default_prefix;
+	} else {
+		prefix = client != NULL && client->prefix != NULL ?
+			client->prefix : log->default_prefix;
+	}
 	client_log_ctx(log, &failure_ctx, log_time, prefix, failure.text);
 }