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From 8866991164690817cc1e3489b6f7aa615170935d Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Nikola=20Forr=C3=B3?= <nforro@redhat.com>
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Date: Wed, 10 Jan 2018 11:38:35 +0100
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Subject: [PATCH] recvmmsg.2, sendmmsg.2: point out that error handling is
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unreliable
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---
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man-pages/man2/recvmmsg.2 | 10 ++++++++++
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man-pages/man2/sendmmsg.2 | 9 +++++++++
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2 files changed, 19 insertions(+)
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diff --git a/man-pages/man2/recvmmsg.2 b/man-pages/man2/recvmmsg.2
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index 4c00ebe..7fc4d5a 100644
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--- a/man-pages/man2/recvmmsg.2
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+++ b/man-pages/man2/recvmmsg.2
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@@ -162,6 +162,8 @@ In addition, the following error can occur:
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.B EINVAL
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.I timeout
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is invalid.
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+.PP
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+See also BUGS.
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.SH VERSIONS
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The
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.BR recvmmsg ()
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@@ -170,6 +172,14 @@ Support in glibc was added in version 2.12.
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.SH CONFORMING TO
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.BR recvmmsg ()
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is Linux-specific.
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+.SH BUGS
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+If an error occurs after at least one message has been received,
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+the call succeeds, and returns the number of messages received.
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+The error code is expected to be returned on a subsequent call to
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+.BR recvmmsq ().
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+In the current implementation, however, the error code can be overwritten
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+in the meantime by an unrelated network event on a socket,
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+for example an incoming ICMP packet.
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.SH EXAMPLE
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.PP
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The following program uses
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diff --git a/man-pages/man2/sendmmsg.2 b/man-pages/man2/sendmmsg.2
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index a646524..939ee3c 100644
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--- a/man-pages/man2/sendmmsg.2
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+++ b/man-pages/man2/sendmmsg.2
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@@ -134,6 +134,7 @@ is set to indicate the error.
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Errors are as for
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.BR sendmsg (2).
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An error is returned only if no datagrams could be sent.
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+See also BUGS.
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.\" commit 728ffb86f10873aaf4abd26dde691ee40ae731fe
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.\" ... only return an error if no datagrams could be sent.
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.\" If less than the requested number of messages were sent, the application
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@@ -165,6 +166,14 @@ is capped to
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.\" For error handling an application using sendmmsg needs to retry at
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.\" the first unsent message, so capping is simpler and requires less
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.\" application logic than returning EINVAL.
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+.SH BUGS
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+If an error occurs after at least one message has been sent,
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+the call succeeds, and returns the number of messages sent.
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+The error code is lost.
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+The caller can retry the transmission,
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+starting at the first failed message, but there is no guarantee that,
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+if an error is returned, it will be the same as the one that was lost
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+on the previous call.
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.SH EXAMPLE
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The example below uses
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.BR sendmmsg ()
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--
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2.13.6
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