gdb/SOURCES/gdb-rhbz881849-ipv6-3of3.patch

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2020-04-23 22:14:15 +00:00
From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
From: Sergio Durigan Junior <sergiodj@redhat.com>
Date: Fri, 3 Aug 2018 18:04:38 -0400
Subject: gdb-rhbz881849-ipv6-3of3.patch
Fix thinko when deciding whether to disable TCP's Nagle algorithm
This patch fixes a thinko that happened when I was implementing the
IPv6 support on GDB/gdbserver. On certain situations, it is necessary
to disable TCP's Nagle algorithm (NODELAY). For obvious reasons, this
only applies when we are dealing with a TCP connection.
While implementing the IPv6 patch, I noticed that the net_open
function (on gdb/ser-tcp.c) kept a flag indicating whether the
connection type was UDP or TCP. I eliminated that flag, and started
using the 'struct addrinfo *' related to the successful connection
directly. However, I made a mistake:
if (success_ainfo->ai_socktype == IPPROTO_TCP)
^^^^^^^^^^^
{
/* Disable Nagle algorithm. Needed in some cases. */
int tmp = 1;
setsockopt (scb->fd, IPPROTO_TCP, TCP_NODELAY,
(char *) &tmp, sizeof (tmp));
}
The 'ai_socktype' field specifies the socket type (SOCK_STREAM or
SOCK_DGRAM), and not the protocol. This test was always failing, and
the Nagle algorithm was never being disabled.
The obvious fix is to use the 'ai_protocol' field. This is what this
patch does.
Huge "thank you" to Joel Brobecker who reported the regression (he was
experiencing an unusual delay while debugging a bare-metal program
running under QEMU) and helped me set up a proper reproducer for the
bug.
gdb/ChangeLog:
2018-08-03 Sergio Durigan Junior <sergiodj@redhat.com>
* ser-tcp.c (net_open): Fix thinko when deciding whether to
disable TCP's Nagle algorithm (use "ai_protocol" instead of
"ai_socktype").
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2018-08-03 Sergio Durigan Junior <sergiodj@redhat.com>
+
+ * ser-tcp.c (net_open): Fix thinko when deciding whether to
+ disable TCP's Nagle algorithm (use "ai_protocol" instead of
+ "ai_socktype").
+
2018-09-05 Joel Brobecker <brobecker@adacore.com>
* version.in: Set GDB version number to 8.2.
diff --git a/gdb/ser-tcp.c b/gdb/ser-tcp.c
--- a/gdb/ser-tcp.c
+++ b/gdb/ser-tcp.c
@@ -367,7 +367,7 @@ net_open (struct serial *scb, const char *name)
ioctl (scb->fd, FIONBIO, &ioarg);
- if (success_ainfo->ai_socktype == IPPROTO_TCP)
+ if (success_ainfo->ai_protocol == IPPROTO_TCP)
{
/* Disable Nagle algorithm. Needed in some cases. */
int tmp = 1;