mac80211: gracefully handle preexisting VIF

Gracefully handle cases where the to-be-created wireless interface already
exists on the system which might commonly happen with non-multi-SSID capable
wireless drivers.

This fixes commit 8301e613655c2d95fa5430a1a57d92d966fdc70b which caused
previously ignored "Too many open files in system (-23)" errors to fail the
wireless setup procedure.

With the updated approach we'll still try recreating the vif after one
second if the first attempt to do so failed with ENFILE but we will now
consider the operation successfull if a second attempt still yields ENFILE
with the requested ifname already existing on the system.

Fixes FS#664, FS#704.

Suggested-by: Vittorio Gambaletta <openwrt@vittgam.net>
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
(cherry picked from commit 4a033475453b63d0d5ae41489e7c395882567698)

diff --git a/package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh b/package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh
index cda6f9f438c89fb78a834c60251c13bd53a10eb6..ebd24df0d3e984bf2afc5997207509f8150509b2 100644 (file)
--- a/package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh
+++ b/package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh
@@ -429,6 +429,12 @@ mac80211_iw_interface_add() {
                rc="$?"
        }
 
+       [ "$rc" = 233 ] && {
+               # Device might not support virtual interfaces, so the interface never got deleted in the first place.
+               # Check if the interface already exists, and avoid failing in this case.
+               ip link show dev "$ifname" >/dev/null 2>/dev/null && rc=0
+       }
+
        [ "$rc" != 0 ] && wireless_setup_failed INTERFACE_CREATION_FAILED
        return $rc
 }