From: "byroot (Jean Boussier)" <noreply@...>
Date: 2022-09-21T08:02:32+00:00
Subject: [ruby-core:109972] [Ruby master Bug#19012] BasicSocket#recv* methods return an empty packet instead of nil on closed connections

Issue #19012 has been updated by byroot (Jean Boussier).


@akr pointed on the PR that this behavior might be desirable for "connection-less" sockets such as `DGRAM`.

That said I think we should try to distinguish between "nothing was received" and "we received an empty packet".

I'm not quite familiar enough with `recv` (yet) to know whether it's possible to make the difference though. I'll try to research this more when I have a bit of time.

----------------------------------------
Bug #19012: BasicSocket#recv* methods return an empty packet instead of nil on closed connections
https://bugs.ruby-lang.org/issues/19012#change-99222

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
`man recvmsg(2)` states:

> Return Value
> These calls return the number of bytes received, or -1 if an error occurred. The return value will be 0 when the peer has performed an orderly shutdown.

But somehow the entire `receiv` family of methods in Ruby seem to interpret `0` as empty string instead of "EOF".

```ruby
require 'socket'

puts "=== pipes ==="
r, w = IO.pipe
r.read_nonblock(1, exception: false) # => :wait_readable
w.close
r.read_nonblock(1, exception: false) # => nil (EOF)

puts "=== sockets ===="
r, w = UNIXSocket.socketpair
r.read_nonblock(1, exception: false) # => :wait_readable
r.recvmsg_nonblock(1, exception: false) # => :wait_readable
r.recv_nonblock(1, exception: false) # => :wait_readable

w.close

r.read_nonblock(1, exception: false) # => nil (EOF)
r.recvmsg_nonblock(1, exception: false) # => ["", #<Addrinfo: empty-sockaddr SOCK_STREAM>, 128]]
r.recvmsg # => ["", #<Addrinfo: empty-sockaddr SOCK_STREAM>, 0]]
r.recv_nonblock(1, exception: false) # => ""
```

### Expected behavior

I would expect `recvmsg_nonblock`, `recvmsg`, `recv_nonblock` and `recv` to return `nil` when the connection is closed.





-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>