From 05952067bb67e3f627c969fd91c9fef29dc7b27e Mon Sep 17 00:00:00 2001
From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Thu, 26 Nov 2020 16:36:50 +0000
Subject: [PATCH] Ensure consistent error messages from ifconfig(8).

If multiple threads are invoking "ifconfig XXX create" a race may occur
which can lead to two different error messages for the same error.

a) ifconfig: SIOCIFCREATE2: File exists
b) ifconfig: interface XXX already exists

This patch ensures ifconfig prints the same error code
for the same case.

Reviewed by:	imp@ and kib@
Differential Revision:	https://reviews.freebsd.org/D27380
MFC after:	1 week
Sponsored by:	Mellanox Technologies // NVIDIA Networking
---
 sbin/ifconfig/ifclone.c     |  3 +--
 sbin/ifconfig/ifconfig.c    | 13 +++++++++++++
 sbin/ifconfig/ifconfig.h    |  1 +
 sbin/ifconfig/ifieee80211.c |  3 +--
 sbin/ifconfig/iflagg.c      |  3 +--
 sbin/ifconfig/ifvlan.c      |  3 +--
 sbin/ifconfig/ifvxlan.c     |  3 +--
 7 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/sbin/ifconfig/ifclone.c b/sbin/ifconfig/ifclone.c
index 58bc3b3103ee..268cc0a28180 100644
--- a/sbin/ifconfig/ifclone.c
+++ b/sbin/ifconfig/ifclone.c
@@ -151,8 +151,7 @@ ifclonecreate(int s, void *arg)
 	}
 	if (clone_cb == NULL) {
 		/* NB: no parameters */
-		if (ioctl(s, SIOCIFCREATE2, &ifr) < 0)
-			err(1, "SIOCIFCREATE2");
+	  	ioctl_ifcreate(s, &ifr);
 	} else {
 		clone_cb(s, &ifr);
 	}
diff --git a/sbin/ifconfig/ifconfig.c b/sbin/ifconfig/ifconfig.c
index e47d0000c7ab..e6e7908e18cd 100644
--- a/sbin/ifconfig/ifconfig.c
+++ b/sbin/ifconfig/ifconfig.c
@@ -198,6 +198,19 @@ usage(void)
 	exit(1);
 }
 
+void
+ioctl_ifcreate(int s, struct ifreq *ifr)
+{
+	if (ioctl(s, SIOCIFCREATE2, ifr) < 0) {
+		switch (errno) {
+		case EEXIST:
+			errx(1, "interface %s already exists", ifr->ifr_name);
+		default:
+			err(1, "SIOCIFCREATE2");
+		}
+	}
+}
+
 #define ORDERS_SIZE(x) sizeof(x) / sizeof(x[0])
 
 static int
diff --git a/sbin/ifconfig/ifconfig.h b/sbin/ifconfig/ifconfig.h
index f91ee2fd23bb..67c25f5921d6 100644
--- a/sbin/ifconfig/ifconfig.h
+++ b/sbin/ifconfig/ifconfig.h
@@ -160,3 +160,4 @@ struct ifmediareq *ifmedia_getstate(int s);
 
 void print_vhid(const struct ifaddrs *, const char *);
 
+void ioctl_ifcreate(int s, struct ifreq *);
diff --git a/sbin/ifconfig/ifieee80211.c b/sbin/ifconfig/ifieee80211.c
index d3f1c3e3aea6..bb406469829a 100644
--- a/sbin/ifconfig/ifieee80211.c
+++ b/sbin/ifconfig/ifieee80211.c
@@ -5758,8 +5758,7 @@ wlan_create(int s, struct ifreq *ifr)
 	    memcmp(params.icp_bssid, zerobssid, sizeof(zerobssid)) == 0)
 		errx(1, "no bssid specified for WDS (use wlanbssid)");
 	ifr->ifr_data = (caddr_t) &params;
-	if (ioctl(s, SIOCIFCREATE2, ifr) < 0)
-		err(1, "SIOCIFCREATE2");
+	ioctl_ifcreate(s, ifr);
 
 	/* XXX preserve original name for ifclonecreate(). */
 	strlcpy(orig_name, name, sizeof(orig_name));
diff --git a/sbin/ifconfig/iflagg.c b/sbin/ifconfig/iflagg.c
index 86532aae3aef..5be8c67cd72a 100644
--- a/sbin/ifconfig/iflagg.c
+++ b/sbin/ifconfig/iflagg.c
@@ -324,8 +324,7 @@ static void
 lagg_create(int s, struct ifreq *ifr)
 {
 	ifr->ifr_data = (caddr_t) &params;
-	if (ioctl(s, SIOCIFCREATE2, ifr) < 0)
-		err(1, "SIOCIFCREATE2");
+	ioctl_ifcreate(s, ifr);
 }
 
 static struct cmd lagg_cmds[] = {
diff --git a/sbin/ifconfig/ifvlan.c b/sbin/ifconfig/ifvlan.c
index bbf9d0324cde..f316b0404459 100644
--- a/sbin/ifconfig/ifvlan.c
+++ b/sbin/ifconfig/ifvlan.c
@@ -162,8 +162,7 @@ vlan_create(int s, struct ifreq *ifr)
 			errx(1, "must specify a parent device for vlan create");
 		ifr->ifr_data = (caddr_t) &params;
 	}
-	if (ioctl(s, SIOCIFCREATE2, ifr) < 0)
-		err(1, "SIOCIFCREATE2");
+	ioctl_ifcreate(s, ifr);
 }
 
 static void
diff --git a/sbin/ifconfig/ifvxlan.c b/sbin/ifconfig/ifvxlan.c
index e9ccc0f4fb2e..fda435343a16 100644
--- a/sbin/ifconfig/ifvxlan.c
+++ b/sbin/ifconfig/ifvxlan.c
@@ -191,8 +191,7 @@ vxlan_create(int s, struct ifreq *ifr)
 	vxlan_check_params();
 
 	ifr->ifr_data = (caddr_t) &params;
-	if (ioctl(s, SIOCIFCREATE2, ifr) < 0)
-		err(1, "SIOCIFCREATE2");
+	ioctl_ifcreate(s, ifr);
 }
 
 static