Ensure we discard unread/unsent data when abandoning a connection attempt.

There are assorted situations wherein PQconnectPoll() will abandon a
connection attempt and try again with different parameters (eg, SSL versus
not SSL).  However, the code forgot to discard any pending data in libpq's
I/O buffers when doing this.  In at least one case (server returns E
message during SSL negotiation), there is unread input data which bollixes
the next connection attempt.  I have not checked to see whether this is
possible in the other cases where we close the socket and retry, but it
seems like a matter of good defensive programming to add explicit
buffer-flushing code to all of them.

This is one of several issues exposed by Daniel Farina's report of
misbehavior after a server-side fork failure.

This has been wrong since forever, so back-patch to all supported branches.

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 75faacb8af728bfa16b878a74ae0c9e8d22d65cd..9727b0cfa553cc3293483ab79b666a6246de97e4 100644 (file)
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1449,6 +1449,9 @@ keep_going:                                               /* We will come back to here until there is
                                                closesocket(conn->sock);
                                                conn->sock = -1;
                                                conn->status = CONNECTION_NEEDED;
+                                               /* Discard any unread/unsent data */
+                                               conn->inStart = conn->inCursor = conn->inEnd = 0;
+                                               conn->outCount = 0;
                                                goto keep_going;
                                        }
                                        else
@@ -1486,6 +1489,9 @@ keep_going:                                               /* We will come back to here until there is
                                                closesocket(conn->sock);
                                                conn->sock = -1;
                                                conn->status = CONNECTION_NEEDED;
+                                               /* Discard any unread/unsent data */
+                                               conn->inStart = conn->inCursor = conn->inEnd = 0;
+                                               conn->outCount = 0;
                                                goto keep_going;
                                        }
                                }
@@ -1599,6 +1605,9 @@ keep_going:                                               /* We will come back to here until there is
                                                closesocket(conn->sock);
                                                conn->sock = -1;
                                                conn->status = CONNECTION_NEEDED;
+                                               /* Discard any unread/unsent data */
+                                               conn->inStart = conn->inCursor = conn->inEnd = 0;
+                                               conn->outCount = 0;
                                                goto keep_going;
                                        }
 
@@ -1666,6 +1675,9 @@ keep_going:                                               /* We will come back to here until there is
                                                closesocket(conn->sock);
                                                conn->sock = -1;
                                                conn->status = CONNECTION_NEEDED;
+                                               /* Discard any unread/unsent data */
+                                               conn->inStart = conn->inCursor = conn->inEnd = 0;
+                                               conn->outCount = 0;
                                                goto keep_going;
                                        }
 
@@ -1685,6 +1697,9 @@ keep_going:                                               /* We will come back to here until there is
                                                closesocket(conn->sock);
                                                conn->sock = -1;
                                                conn->status = CONNECTION_NEEDED;
+                                               /* Discard any unread/unsent data */
+                                               conn->inStart = conn->inCursor = conn->inEnd = 0;
+                                               conn->outCount = 0;
                                                goto keep_going;
                                        }
 #endif