content interface behaves different if tried an operation before connecting the interface

[Roberto Mier Escandon]

I've got a wifi-connect snap which has an application using content interface to get use of wifi-ap exposed $SNAP_DATA/sockets directory.
Depending on the order of the steps I take, the behaviour of the app run is different resulting in denial or success:

CASE A:
STEPS:
1- have neither wifi-ap or wifi-connect snaps installed
2- install wifi-ap from store
3- install our wifi-connect snap in strict mode
 snap install wifi-connect_0.1_amd64.snap --dangerous
6- connect control interface
 snap connect wifi-connect:control wifi-ap:control
7- run
 sudo wifi-connect.wifi-ap -show
8 got a denial in syslog traces and this response:
 Error: '"/snap/wifi-connect/x1/bin/unixhttpc" ["/var/snap/wifi-ap/current/sockets/control" "/v1/configuration"]' failed. "exit status 2"

That makes sense as wifi-connect tries to mount content share in rw mode into $SNAP/snap/sockets which is read only

CASE B:
STEPS:
1- have neither wifi-ap or wifi-connect snaps installed
2- install wifi-ap from store
3- install our wifi-connect snap in strict mode
 snap install wifi-connect_0.1_amd64.snap --dangerous
4- run
 sudo wifi-connect.wifi-ap -show
5- got a denial in syslog traces and this response:
 Error: '"/snap/wifi-connect/x1/bin/unixhttpc" ["/var/snap/wifi-ap/current/sockets/control" "/v1/configuration"]' failed. "exit status 2"
6- connect control interface
 snap connect wifi-connect:control wifi-ap:control
7- run
 sudo wifi-connect.wifi-ap -show

EXPECTED:
- same denial and result as step 5, as wifi-connect tries to mount content share in rw mode into $SNAP/snap/sockets which is read only

RESULT:
- got this succesful reply
Wifi-ap Configuration:
Unix HTTP client
{"result":{"debug":false,"dhcp.lease-time":"12h","dhcp.range-start":"10.0.60.2","dhcp.range-stop":"10.0.60.199","disabled":false,"share.disabled":false,"share.network-interface":"enx9cebe8163f7d","wifi.address":"10.0.60.1","wifi.channel":"6","wifi.hostapd-driver":"nl80211","wifi.interface":"wlan0","wifi.interface-mode":"direct","wifi.netmask":"255.255.255.0","wifi.operation-mode":"g","wifi.security":"open","wifi.security-passphrase":"","wifi.ssid":"Ubuntu"},"status":"OK","status-code":200,"type":"sync"}

- Anytime from now on you execute the operation, it works.

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attached is wifi-connect snap used for this. You can find the source code for it in here [1]

[1] https://github.com/rmescandon/UCWifiConnect/tree/unixhttpc-src

[Zygmunt Krynicki (zyga)]

This is a known issue that is being tracked https://github.com/snapcore/snapd/projects/1