Re: crash bug on closed connection - Mailing list pgsql-odbc

Some of these steps might not be necessary. It might could be accomplished with a kill -9 on postgres. I tried running Postgres on Windows, and force killing it, but then the client always knew the connection was down.

When this occurs "in the wild", it is usually related to a timeout, so the fix that was checked in recently for setting tcpKeepAlive might be a workaround.

On Mon, Oct 13, 2014 at 4:44 PM, Jade Koskela <jkoskela0@gmail.com> wrote:

I have been looking into this crash for a while now, and I finally have a good repro.

After digging through it with wireshark I observed this

client tries to send a query

 retransmit query

 retransmit query

 ...

client sends TCP [RST],[ACK]

Now it has crashed, so we restart it again and begin another connection successfully.

It seems that the connection has dropped, but the client was never informed, and it doesn't handle this gracefully. 

I reproed it like this:

On my mac running postgres server:

  Setup port forwarding to emulate a proxy or firewall problem

  ssh -L [public ip]:5433:localhost:5432 -N localhost

On my windows machine:

  Connect to port 5433 on my mac

  Run a query

On my mac:

  Kill the ssh proxy

  sighup postgres

  open the ssh proxy again

On my windows machine:

  Run another query (machine still thinks connection is ok)

  Crash in psqlodbcw.dll   

> psqlodbc35w.dll!Exec_with_parameters_resolved(StatementClass_ * stmt=0x0a6f4fa0, int * exec_end=0x083bf3dc)  Line 606 + 0x1b bytes C

  psqlodbc35w.dll!PGAPI_Execute(void * hstmt=0x0a6f4fa0, unsigned short flag=1)  Line 1147 + 0xd bytes C

  psqlodbc35w.dll!SQLExecute(void * StatementHandle=0x0a6f4fa0)  Line 386 + 0xe bytes C

  odbc32.dll!_SQLExecute@4()  + 0x2c1 bytes

> if (sscanf(cmd , "UPDATE %d", &count) == 1) // here cmd is junk but not null (0xddddddd)