Don't log incomplete startup packet if it's empty

This will stop logging cases where, for example, a monitor opens a
connection and immediately closes it. If the packet contains any data an
incomplete packet will still be logged.

Author: Tom Lane

Discussion: https://postgr.es/m/a1379a72-2958-1ed0-ef51-09a21219b155@2ndQuadrant.com

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index ccea231e985805cf9e7c34d3cbf36a260831437b..fe599632d3d478554a4e51b9189dac673433f4b5 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -1899,17 +1899,34 @@ ProcessStartupPacket(Port *port, bool SSLdone)
        MemoryContext oldcontext;
 
        pq_startmsgread();
-       if (pq_getbytes((char *) &len, 4) == EOF)
+
+       /*
+        * Grab the first byte of the length word separately, so that we can tell
+        * whether we have no data at all or an incomplete packet.  (This might
+        * sound inefficient, but it's not really, because of buffering in
+        * pqcomm.c.)
+        */
+       if (pq_getbytes((char *) &len, 1) == EOF)
        {
                /*
-                * EOF after SSLdone probably means the client didn't like our
-                * response to NEGOTIATE_SSL_CODE.  That's not an error condition, so
-                * don't clutter the log with a complaint.
+                * If we get no data at all, don't clutter the log with a complaint;
+                * such cases often occur for legitimate reasons.  An example is that
+                * we might be here after responding to NEGOTIATE_SSL_CODE, and if the
+                * client didn't like our response, it'll probably just drop the
+                * connection.  Service-monitoring software also often just opens and
+                * closes a connection without sending anything.  (So do port
+                * scanners, which may be less benign, but it's not really our job to
+                * notice those.)
                 */
-               if (!SSLdone)
-                       ereport(COMMERROR,
-                                       (errcode(ERRCODE_PROTOCOL_VIOLATION),
-                                        errmsg("incomplete startup packet")));
+               return STATUS_ERROR;
+       }
+
+       if (pq_getbytes(((char *) &len) + 1, 3) == EOF)
+       {
+               /* Got a partial length word, so bleat about that */
+               ereport(COMMERROR,
+                               (errcode(ERRCODE_PROTOCOL_VIOLATION),
+                                errmsg("incomplete startup packet")));
                return STATUS_ERROR;
        }