net: stmmac: don't reject VLANs when IFF_PROMISC is set
[ Upstream commit a7602e73 ] The blamed commit has introduced the following tests to dwmac4_add_hw_vlan_rx_fltr(), called from stmmac_vlan_rx_add_vid(): if (hw->promisc) { netdev_err(dev, "Adding VLAN in promisc mode not supported\n"); return -EPERM; } "VLAN promiscuous" mode is keyed in this driver to IFF_PROMISC, and so, vlan_vid_add() and vlan_vid_del() calls cannot take place in IFF_PROMISC mode. I have the following 2 arguments that this restriction is.... hm, how shall I put it nicely... unproductive :) First, take the case of a Linux bridge. If the kernel is compiled with CONFIG_BRIDGE_VLAN_FILTERING=y, then this bridge shall have a VLAN database. The bridge shall try to call vlan_add_vid() on its bridge ports for each VLAN in the VLAN table. It will do this irrespectively of whether that port is *currently* VLAN-aware or not. So it will do this even when the bridge was created with vlan_filtering 0. But the Linux bridge, in VLAN-unaware mode, configures its ports in promiscuous (IFF_PROMISC) mode, so that they accept packets with any MAC DA (a switch must do this in order to forward those packets which are not directly targeted to its MAC address). As a result, the stmmac driver does not work as a bridge port, when the kernel is compiled with CONFIG_BRIDGE_VLAN_FILTERING=y. $ ip link add br0 type bridge && ip link set br0 up $ ip link set eth0 master br0 && ip link set eth0 up [ 2333.943296] br0: port 1(eth0) entered blocking state [ 2333.943381] br0: port 1(eth0) entered disabled state [ 2333.943782] device eth0 entered promiscuous mode [ 2333.944080] 4033c000.ethernet eth0: Adding VLAN in promisc mode not supported [ 2333.976509] 4033c000.ethernet eth0: failed to initialize vlan filtering on this port RTNETLINK answers: Operation not permitted Secondly, take the case of stmmac as DSA master. Some switch tagging protocols are based on 802.1Q VLANs (tag_sja1105.c), and as such, tag_8021q.c uses vlan_vid_add() to work with VLAN-filtering DSA masters. But also, when a DSA port becomes promiscuous (for example when it joins a bridge), the DSA framework also makes the DSA master promiscuous. Moreover, for every VLAN that a DSA switch sends to the CPU, DSA also programs a VLAN filter on the DSA master, because if the the DSA switch uses a tail tag, then the hardware frame parser of the DSA master will see VLAN as VLAN, and might filter them out, for being unknown. Due to the above 2 reasons, my belief is that the stmmac driver does not get to choose to not accept vlan_vid_add() calls while IFF_PROMISC is enabled, because the 2 are completely independent and there are code paths in the network stack which directly lead to this situation occurring, without the user's direct input. In fact, my belief is that "VLAN promiscuous" mode should have never been keyed on IFF_PROMISC in the first place, but rather, on the NETIF_F_HW_VLAN_CTAG_FILTER feature flag which can be toggled by the user through ethtool -k, when present in netdev->hw_features. In the stmmac driver, NETIF_F_HW_VLAN_CTAG_FILTER is only present in "features", making this feature "on [fixed]". I have this belief because I am unaware of any definition of promiscuity which implies having an effect on anything other than MAC DA (therefore not VLAN). However, I seem to be rather alone in having this opinion, looking back at the disagreements from this discussion: https://lore.kernel.org/netdev/20201110153958.ci5ekor3o2ekg3ky@ipetronik.com/ In any case, to remove the vlan_vid_add() dependency on !IFF_PROMISC, one would need to remove the check and see what fails. I guess the test was there because of the way in which dwmac4_vlan_promisc_enable() is implemented. For context, the dwmac4 supports Perfect Filtering for a limited number of VLANs - dwmac4_get_num_vlan(), priv->hw->num_vlan, with a fallback on Hash Filtering - priv->dma_cap.vlhash - see stmmac_vlan_update(), also visible in cat /sys/kernel/debug/stmmaceth/eth0/dma_cap | grep 'VLAN Hash Filtering'. The perfect filtering is based on MAC_VLAN_Tag_Filter/MAC_VLAN_Tag_Data registers, accessed in the driver through dwmac4_write_vlan_filter(). The hash filtering is based on the MAC_VLAN_Hash_Table register, named GMAC_VLAN_HASH_TABLE in the driver and accessed by dwmac4_update_vlan_hash(). The control bit for enabling hash filtering is GMAC_VLAN_VTHM (MAC_VLAN_Tag_Ctrl bit VTHM: VLAN Tag Hash Table Match Enable). Now, the description of dwmac4_vlan_promisc_enable() is that it iterates through the driver's cache of perfect filter entries (hw->vlan_filter[i], added by dwmac4_add_hw_vlan_rx_fltr()), and evicts them from hardware by unsetting their GMAC_VLAN_TAG_DATA_VEN (MAC_VLAN_Tag_Data bit VEN - VLAN Tag Enable) bit. Then it unsets the GMAC_VLAN_VTHM bit, which disables hash matching. This leaves the MAC, according to table "VLAN Match Status" from the documentation, to always enter these data paths: VID |VLAN Perfect Filter |VTHM Bit |VLAN Hash Filter |Final VLAN Match |Match Result | |Match Result |Status -------|--------------------|---------|-----------------|---------------- VID!=0 |Fail |0 |don't care |Pass So, dwmac4_vlan_promisc_enable() does its job, but by unsetting GMAC_VLAN_VTHM, it conflicts with the other code path which controls this bit: dwmac4_update_vlan_hash(), called through stmmac_update_vlan_hash() from stmmac_vlan_rx_add_vid() and from stmmac_vlan_rx_kill_vid(). This is, I guess, why dwmac4_add_hw_vlan_rx_fltr() is not allowed to run after dwmac4_vlan_promisc_enable() has unset GMAC_VLAN_VTHM: because if it did, then dwmac4_update_vlan_hash() would set GMAC_VLAN_VTHM again, breaking the "VLAN promiscuity". It turns out that dwmac4_vlan_promisc_enable() is way too complicated for what needs to be done. The MAC_Packet_Filter register also has the VTFE bit (VLAN Tag Filter Enable), which simply controls whether VLAN tagged packets which don't match the filtering tables (either perfect or hash) are dropped or not. At the moment, this driver unconditionally sets GMAC_PACKET_FILTER_VTFE if NETIF_F_HW_VLAN_CTAG_FILTER was detected through the priv->dma_cap.vlhash capability bits of the device, in stmmac_dvr_probe(). I would suggest deleting the unnecessarily complex logic from dwmac4_vlan_promisc_enable(), and simply unsetting GMAC_PACKET_FILTER_VTFE when becoming IFF_PROMISC, which has the same effect of allowing packets with any VLAN tags, but has the additional benefit of being able to run concurrently with stmmac_vlan_rx_add_vid() and stmmac_vlan_rx_kill_vid(). As much as I believe that the VTFE bit should have been exclusively controlled by NETIF_F_HW_VLAN_CTAG_FILTER through ethtool, and not by IFF_PROMISC, changing that is not a punctual fix to the problem, and it would probably break the VFFQ feature added by the later commit e0f9956a ("net: stmmac: Add option for VLAN filter fail queue enable"). From the commit description, VFFQ needs IFF_PROMISC=on and VTFE=off in order to work (and this change respects that). But if VTFE was changed to be controlled through ethtool -k, then a user-visible change would have been introduced in Intel's scripts (a need to run "ethtool -k eth0 rx-vlan-filter off" which did not exist before). The patch was tested with this set of commands: ip link set eth0 up ip link add link eth0 name eth0.100 type vlan id 100 ip addr add 192.168.100.2/24 dev eth0.100 && ip link set eth0.100 up ip link set eth0 promisc on ip link add link eth0 name eth0.101 type vlan id 101 ip addr add 192.168.101.2/24 dev eth0.101 && ip link set eth0.101 up ip link set eth0 promisc off ping -c 5 192.168.100.1 ping -c 5 192.168.101.1 ip link set eth0 promisc on ping -c 5 192.168.100.1 ping -c 5 192.168.101.1 ip link del eth0.100 ip link del eth0.101 # Wait for VLAN-tagged pings from the other end... # Check with "tcpdump -i eth0 -e -n -p" and we should see them ip link set eth0 promisc off # Wait for VLAN-tagged pings from the other end... # Check with "tcpdump -i eth0 -e -n -p" and we shouldn't see them # anymore, but remove the "-p" argument from tcpdump and they're there. Fixes: c89f44ff ("net: stmmac: Add support for VLAN promiscuous mode") Signed-off-by:Vladimir Oltean <vladimir.oltean@nxp.com> Signed-off-by:
Please register or sign in to comment