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