File 2602-erts-Limit-the-automatic-max-buffer-for-UDP-to-2-16.patch of Package erlang
From a9d361b4be7d6329bedd7b37d454c1abf4f27233 Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang.org>
Date: Thu, 21 Jun 2018 11:00:25 +0200
Subject: [PATCH 2/2] erts: Limit the automatic max buffer for UDP to 2^16
There is no reason to have a larger buffer than this as
the recvmsg call will never return more data.
OTP-15206
---
erts/emulator/drivers/common/inet_drv.c | 9 ++++++++-
lib/kernel/doc/src/inet.xml | 19 ++++++++++---------
lib/kernel/test/gen_udp_SUITE.erl | 12 ++++++++++--
3 files changed, 28 insertions(+), 12 deletions(-)
diff --git a/erts/emulator/drivers/common/inet_drv.c b/erts/emulator/drivers/common/inet_drv.c
index 833befefd1..2048d0f625 100644
--- a/erts/emulator/drivers/common/inet_drv.c
+++ b/erts/emulator/drivers/common/inet_drv.c
@@ -1549,6 +1549,8 @@ static void *realloc_wrapper(void *current, ErlDrvSizeT size){
# define LOAD_ASSOC_ID LOAD_UINT
# define LOAD_ASSOC_ID_CNT LOAD_UINT_CNT
# define SCTP_ANC_BUFF_SIZE INET_DEF_BUFFER/2 /* XXX: not very good... */
+#else
+# define IS_SCTP(desc) 0
#endif
#ifdef HAVE_UDP
@@ -6436,7 +6438,12 @@ static int inet_set_opts(inet_descriptor* desc, char* ptr, int len)
(long)desc->port, desc->s, res));
if (type == SO_RCVBUF) {
/* make sure we have desc->bufsz >= SO_RCVBUF */
- if (ival > desc->bufsz)
+ if (ival > (1 << 16) && desc->stype == SOCK_DGRAM && !IS_SCTP(desc))
+ /* For UDP we don't want to automatically
+ set the buffer size to be larger than
+ the theoretical max MTU */
+ desc->bufsz = 1 << 16;
+ else if (ival > desc->bufsz)
desc->bufsz = ival;
}
}
diff --git a/lib/kernel/doc/src/inet.xml b/lib/kernel/doc/src/inet.xml
index e6a7962c5a..f281d61459 100644
--- a/lib/kernel/doc/src/inet.xml
+++ b/lib/kernel/doc/src/inet.xml
@@ -734,22 +734,23 @@ get_tcpi_sacked(Sock) ->
</item>
<tag><c>{buffer, Size}</c></tag>
<item>
- <p>The size of the user-level software buffer used by
- the driver.
- Not to be confused with options <c>sndbuf</c>
+ <p>The size of the user-level buffer used by
+ the driver. Not to be confused with options <c>sndbuf</c>
and <c>recbuf</c>, which correspond to the
- Kernel socket buffers. It is recommended
- to have <c>val(buffer) >= max(val(sndbuf),val(recbuf))</c> to
+ Kernel socket buffers. For TCP it is recommended
+ to have <c>val(buffer) >= val(recbuf)</c> to
avoid performance issues because of unnecessary copying.
+ For UDP the same recommendation applies, but the max should
+ not be larger than the MTU of the network path.
<c>val(buffer)</c> is automatically set to the above
- maximum when values <c>sndbuf</c> or <c>recbuf</c> are set.
- However, as the sizes set for <c>sndbuf</c> and <c>recbuf</c>
+ maximum when <c>recbuf</c> is set.
+ However, as the size set for <c>recbuf</c>
usually become larger, you are encouraged to use
<seealso marker="#getopts/2"><c>getopts/2</c></seealso>
to analyze the behavior of your operating system.</p>
<p>Note that this is also the maximum amount of data that can be
- received from a single recv call. If you are using higher than
- normal MTU consider setting buffer higher.</p>
+ received from a single recv call. If you are using higher than
+ normal MTU consider setting buffer higher.</p>
</item>
<tag><c>{delay_send, Boolean}</c></tag>
<item>
diff --git a/lib/kernel/test/gen_udp_SUITE.erl b/lib/kernel/test/gen_udp_SUITE.erl
index b39399b18a..3acfff929e 100644
--- a/lib/kernel/test/gen_udp_SUITE.erl
+++ b/lib/kernel/test/gen_udp_SUITE.erl
@@ -34,7 +34,7 @@
-export([init_per_testcase/2, end_per_testcase/2]).
-export([send_to_closed/1, active_n/1,
- buffer_size/1, binary_passive_recv/1, bad_address/1,
+ buffer_size/1, binary_passive_recv/1, max_buffer_size/1, bad_address/1,
read_packets/1, recv_poll_after_active_once/1,
open_fd/1, connect/1, implicit_inet6/1,
local_basic/1, local_unbound/1,
@@ -50,6 +50,7 @@ suite() ->
send_to_closed,
buffer_size,
binary_passive_recv,
+ max_buffer_size,
bad_address,
read_packets,
recv_poll_after_active_once,
@@ -260,6 +261,14 @@ buffer_size_server_recv(Socket, IP, Port, Cnt) ->
end.
+%%-------------------------------------------------------------
+%% OTP-15206: Keep buffer small for udp
+%%-------------------------------------------------------------
+max_buffer_size(Config) when is_list(Config) ->
+ {ok, Socket} = gen_udp:open(0, [binary]),
+ ok = inet:setopts(Socket,[{recbuf, 1 bsl 20}]),
+ {ok, [{buffer, 65536}]} = inet:getopts(Socket,[buffer]),
+ gen_udp:close(Socket).
%%-------------------------------------------------------------
%% OTP-3823 gen_udp:recv does not return address in binary mode
--
2.16.4
