From 8cd9718f0b29edf380e35ac462773c26ab2a729c Mon Sep 17 00:00:00 2001
From: Gleb Smirnoff <glebius@FreeBSD.org>
Date: Wed, 4 Mar 2020 22:27:16 +0000
Subject: When a machine boots the NFS mounting script is executed after
 interfaces are configured, but for many interfaces (e.g. all Intel) ifconfig
 causes link renegotiation, so the first attempt to mount NFS always fails.
 After that mount_nfs sleeps for 30 seconds, while only a couple seconds are
 actually required for interface to get up.

Instead of sleeping, do select(2) on routing socket and check if
some interface became UP and in this case retry immediately.

Reviewed by:	rmacklem
Differential Revision:	https://reviews.freebsd.org/D23934
---
 sbin/mount_nfs/mount_nfs.c | 62 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

(limited to 'sbin/mount_nfs')

diff --git a/sbin/mount_nfs/mount_nfs.c b/sbin/mount_nfs/mount_nfs.c
index 1c15f505d8ec..8d8ddac62224 100644
--- a/sbin/mount_nfs/mount_nfs.c
+++ b/sbin/mount_nfs/mount_nfs.c
@@ -65,6 +65,8 @@ __FBSDID("$FreeBSD$");
 #include <fs/nfs/nfsv4_errstr.h>
 
 #include <arpa/inet.h>
+#include <net/route.h>
+#include <net/if.h>
 
 #include <ctype.h>
 #include <err.h>
@@ -505,6 +507,59 @@ sec_num_to_name(int flavor)
 	return (NULL);
 }
 
+/*
+ * Wait for RTM_IFINFO message with interface that is IFF_UP and with
+ * link on, or until timeout expires.  Returns seconds left.
+ */
+static time_t
+rtm_ifinfo_sleep(time_t sec)
+{
+	char buf[2048];
+	fd_set rfds;
+	struct timeval tv, start;
+	ssize_t nread;
+	int n, s;
+
+	s = socket(PF_ROUTE, SOCK_RAW, 0);
+	if (s < 0)
+		err(EX_OSERR, "socket");
+	(void)gettimeofday(&start, NULL);
+
+	for (tv.tv_sec = sec, tv.tv_usec = 0;
+	    tv.tv_sec > 0;
+	    (void)gettimeofday(&tv, NULL),
+	    tv.tv_sec = sec - (tv.tv_sec - start.tv_sec)) {
+		FD_ZERO(&rfds);
+		FD_SET(s, &rfds);
+		n = select(s + 1, &rfds, NULL, NULL, &tv);
+		if (n == 0)
+			continue;
+		if (n == -1) {
+			if (errno == EINTR)
+				continue;
+			else
+				err(EX_SOFTWARE, "select");
+		}
+		nread = read(s, buf, 2048);
+		if (nread < 0)
+			err(EX_OSERR, "read");
+		if ((size_t)nread >= sizeof(struct if_msghdr)) {
+			struct if_msghdr *ifm;
+
+			ifm = (struct if_msghdr *)buf;
+			if (ifm->ifm_version == RTM_VERSION &&
+			    ifm->ifm_type == RTM_IFINFO &&
+			    (ifm->ifm_flags & IFF_UP) &&
+			    ifm->ifm_data.ifi_link_state != LINK_STATE_DOWN)
+				break;
+		}
+	}
+
+	close(s);
+
+	return (tv.tv_sec);
+}
+
 static int
 getnfsargs(char *spec, struct iovec **iov, int *iovlen)
 {
@@ -638,7 +693,12 @@ getnfsargs(char *spec, struct iovec **iov, int *iovlen)
 			if (daemon(0, 0) != 0)
 				err(1, "daemon");
 		}
-		sleep(60);
+		/*
+		 * If rtm_ifinfo_sleep() returns non-zero, don't count
+		 * that as a retry attempt.
+		 */
+		if (rtm_ifinfo_sleep(60) && retrycnt != 0)
+			retrycnt++;
 	}
 	freeaddrinfo(ai_nfs);
 
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