[agroal#392] Add application name and version in management protocol

In order to improve debugging, [agroal#392] suggested to write
the sender application name and its version into the header
over which pgagroal-cli and pgagroal communicate.

Introduces the 'write_header_info' function in
management.c.

src/libpgagroal/management.c

@@ -52,13 +52,14 @@
 #include <openssl/err.h>
 #include <openssl/ssl.h>
 
-#define MANAGEMENT_HEADER_SIZE 5
+#define MANAGEMENT_HEADER_SIZE 60
 
 static int read_complete(SSL* ssl, int socket, void* buf, size_t size);
 static int write_complete(SSL* ssl, int socket, void* buf, size_t size);
 static int write_socket(int socket, void* buf, size_t size);
 static int write_ssl(SSL* ssl, void* buf, size_t size);
 static int write_header(SSL* ssl, int fd, signed char type, int slot);
+static int write_header_info(char* header, bool start, char* command);
 
 static int pgagroal_management_write_conf_ls_detail(int socket, char* what);
 static int pgagroal_management_read_conf_ls_detail(SSL* ssl, int socket, char* buffer);
@@ -1113,10 +1114,12 @@ pgagroal_management_read_isalive(SSL* ssl, int socket, int* status, char output_
 int
 pgagroal_management_write_isalive(int socket, bool gracefully)
 {
-   char buf[4];
+   char buf[MANAGEMENT_HEADER_SIZE];
 
    memset(&buf, 0, sizeof(buf));
 
+   write_header_info(buf, 1, "pgagroal ");
+
    if (!gracefully)
    {
       pgagroal_write_int32(buf, PING_STATUS_RUNNING);
@@ -1610,6 +1613,27 @@ write_ssl(SSL* ssl, void* buf, size_t size)
    return 1;
 }
 
+static int
+write_header_info(char* header, bool start, char* command) {
+   char header_info[42] = " {sender: ";
+
+   strcat(header_info, command);
+   strcat(header_info, "version: ");
+   strcat(header_info, PGAGROAL_VERSION);
+   strcat(header_info, "}");
+
+   if (start) {
+      pgagroal_write_string(header, header_info);
+   }
+   else {
+      pgagroal_write_string(header + 4, header_info);
+   }
+
+   pgagroal_log_debug("Header: %s\n", header);
+
+   return 0;
+}
+
 static int
 write_header(SSL* ssl, int fd, signed char type, int slot)
 {
@@ -1618,6 +1642,8 @@ write_header(SSL* ssl, int fd, signed char type, int slot)
    pgagroal_write_byte(&(header), type);
    pgagroal_write_int32(&(header[1]), slot);
 
+   write_header_info(header, 0 ,"pgagroal-cli ");
+
    return write_complete(ssl, fd, &(header), MANAGEMENT_HEADER_SIZE);
 }