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List:       busybox
Subject:    [PATCH 4/8] mdev: re-initialize if uevent messages were lost
From:       Jan Klötzke <jan () kloetzke ! net>
Date:       2019-12-16 21:56:52
Message-ID: 20191216215656.6438-5-jan () kloetzke ! net
[Download RAW message or body]

If the netlink read() failed with ENOBUFS we know that we have missed at
least one message due to a socket receive buffer overrun. The only way
how to recover is to drop the old socket, open a fresh one and make a
cold-plug scan of the current system state.

Signed-off-by: Jan Klötzke <jan@kloetzke.net>
---
 util-linux/mdev.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/util-linux/mdev.c b/util-linux/mdev.c
index cfc1a38bc..91c4ff466 100644
--- a/util-linux/mdev.c
+++ b/util-linux/mdev.c
@@ -1206,6 +1206,16 @@ static void daemon_loop(char *temp, int fd)
 
 		len = safe_read(fd, netbuf, sizeof(netbuf) - 1);
 		if (len < 0) {
+			if (errno == ENOBUFS) {
+				/*
+				 * We ran out of socket receive buffer space.
+				 * Start from scratch.
+				 */
+				dbg1s("uevent overrun! Rescanning...");
+				close(fd);
+				fd = daemon_init(temp);
+				continue;
+			}
 			bb_simple_perror_msg_and_die("read");
 		}
 		end = netbuf + len;
-- 
2.20.1

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