Bug #11701: recvmsg for UDP without argument

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN

[akr (Akira Tanaka)]

It seems recvmsg without argument doesn't work well for UDP now.

Following example sends a packet which size is 10000 bytes but
receives a packet which size is 4096 bytes.

% ./ruby -rsocket -ve 's1 = Addrinfo.udp("127.0.0.1", 0).bind             
s2 = s1.connect_address.connect
s2.send("a"*10000, 0)
ret = s1.recvmsg
p ret[0].length
'
ruby 2.3.0dev (2015-11-17 trunk 52613) [x86_64-linux]
4096

ruby-2.3.0-preview1 worked well.
It receives a packet which size is 10000 bytes.

% ruby-2.3.0-preview1 -rsocket -ve 's1 = Addrinfo.udp("127.0.0.1", 0).bind
s2 = s1.connect_address.connect
s2.send("a"*10000, 0)
ret = s1.recvmsg
p ret[0].length
'
ruby 2.3.0preview1 (2015-11-11 trunk 52539) [x86_64-linux]
10000

This behavior (recvmsg without arguments) is documented as follows:

maxmesglen and maxcontrollen can
be nil. In that case, the buffer will be grown until the message is not
truncated. Internally, MSG_PEEK is used and MSG_TRUNC/MSG_CTRUNC are checked.

[normalperson (Eric Wong)]

[e-mail] wrote:

Bug #11701: recvmsg for UDP without argument
https://bugs.ruby-lang.org/issues/11701

Oops, will take a look...

• Status changed from Open to Closed

Applied in changeset r52625.

---

socket: fix recvmsg without argument

• ext/socket/ancdata.c (bsock_recvmsg_internal): grow buffer
  on unspecified maxdatlen
  [ruby-core:71517] [Bug #11701]
• ext/socket/lib/socket.rb (Socket#recvmsg): nil default for dlen
  (Socket#recvmsg_nonblock): ditto
• test/socket/test_socket.rb (test_recvmsg_udp_no_arg): new test