What does ECONNABORTED mean when trying to connect a socket?

Question

I'm using python 2.7 on an ubuntu machine.

The client tries to connect to the server. I get a EINPROGRESS which is expected for non-blocking sockets.

To check whether or not the connection succeeded, I do what the man page for {connect} suggest:

# EINPROGRESS The socket is nonblocking and the connection cannot be
# completed immediately.  It is possible to select(2) or poll(2) for
# completion by selecting the socket for writing.  After select(2)
# indicates writability, use getsockopt(2) to read the SO_ERROR option at
# level SOL_SOCKET to determine whether connect() completed successfully
# (SO_ERROR is zero) or unsuccessfully (SO_ERROR is one of the usual error
# codes listed here, explaining the reason for the failure)

When the server is offline, this gives me a ECONNREFUSED. So far so good.

When the connection fails, I want to try again a few times.

Problem: the second time I try to connect that same socket, {connect} sends me ECONNABORTED. This one isn't in the man page of {connect}. What does it mean?

Answer 1

ECONNABORTED is set in two places of the Linux Kernel Source Socket Code.

As per the errno man page and /include/asm-generic/errno.h

#define ECONNABORTED 103 /* Software caused connection abort */

The first is in the function that defines the syscall accept4 in /net/socket.c.

Relevant Source Code

1533         if (upeer_sockaddr) {
1534                 if (newsock->ops->getname(newsock, (struct sockaddr *)&address,
1535                                           &len, 2) < 0) {
1536                         err = -ECONNABORTED;
1537                         goto out_fd;
1538                 }
1539                 err = move_addr_to_user((struct sockaddr *)&address,
1540                                         len, upeer_sockaddr, upeer_addrlen);
1541                 if (err < 0)
1542                         goto out_fd;
1543         }

The relevant explanation of logic is below.

If the address of the peer socket from userspace is defined and If the new socket doesn't have name, then set error state to ECONNABORTED and goto the label out_fd.

The second is in the function that defines the symbol inet_stream_connect in /net/ipv4/af_inet.c.

Relevant Source Code

645         /* Connection was closed by RST, timeout, ICMP error
646          * or another process disconnected us.
647          */
648         if (sk->sk_state == TCP_CLOSE)
649                 goto sock_error; 

662 sock_error:
663         err = sock_error(sk) ? : -ECONNABORTED;
664         sock->state = SS_UNCONNECTED;
665         if (sk->sk_prot->disconnect(sk, flags))
666                 sock->state = SS_DISCONNECTING;
667         goto out;

The relevant explanation of logic is below.

The only code that has a goto to the sock_error label in inet_stream_connect is the check to see if the socket was closed by RST,timeout, another process or error.

In the sock_error label If we can recover a socket error report, do so , otherwise the error state to ECONNABORTED

Like Celada's comment I also recommend opening a new socket each time.