SSHD port forwarding. Channel closed abruptly on remote socket error

After creating a connection to a remote server using port forwarding, is the remote server close the socket suddenly, sshd perform a channel close wihtout sending a SSH_MSG_CHANNEL_CLOSE to the ssh client.

Moreover (see SSHD-795) ifa failure is happening during write, the connection to ssh client is suddenly (and wrongly) closed.

Attached a possible patch for the problem.