[PATCH net-next 00/10] Doc: update bridge doc

[PATCH net-next 00/10] Doc: update bridge doc

[Hangbin Liu]

The current bridge kernel doc is too old. It only pointed to the
linuxfoundation wiki page which lacks of the new features.

Here let's start the new bridge document and put all the bridge info
so new developers and users could catch up the last bridge status soon.

Something I'd like to do in the future:
  - add iproute2 cmd examples for each feature

RFCv3 -> v1:
- Fix up various typos, grammar and technical issues (Nikolay Aleksandrov)

RFCv2 -> RFCv3:
- Update netfilter part (Florian Westphal)
- Break the one large patch in to multiparts for easy reviewing. Please tell
  me if I break it too much.. (Nikolay Aleksandrov)
- Update the description of each enum and doc (Nikolay Aleksandrov)
- Add more descriptions for STP/Multicast/VLAN.

RFCv1 -> RFCv2:
- Drop the python tool that generate iproute man page from kernel doc

Hangbin Liu (10):
  net: bridge: add document for IFLA_BR enum
  net: bridge: add document for IFLA_BRPORT enum
  net: bridge: add document for bridge sysfs attribute
  docs: bridge: Add kAPI/uAPI fields
  docs: bridge: add STP doc
  docs: bridge: add VLAN doc
  docs: bridge: add multicast doc
  docs: bridge: add switchdev doc
  docs: bridge: add netfilter doc
  docs: bridge: add other features

 Documentation/networking/bridge.rst | 321 +++++++++++++++++-
 include/uapi/linux/if_link.h        | 500 ++++++++++++++++++++++++++++
 net/bridge/br_private.h             |   2 +
 net/bridge/br_sysfs_br.c            |  93 ++++++
 4 files changed, 906 insertions(+), 10 deletions(-)

-- 
2.41.0

[PATCH net-next 01/10] net: bridge: add document for IFLA_BR enum

[Hangbin Liu]

Add document for IFLA_BR enum so we can use it in
Documentation/networking/bridge.rst.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 include/uapi/linux/if_link.h | 278 +++++++++++++++++++++++++++++++++++
 1 file changed, 278 insertions(+)

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 8181ef23a7a2..8debf1c62a6d 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -461,6 +461,284 @@ enum in6_addr_gen_mode {
 
 /* Bridge section */
 
+/**
+ * DOC: Bridge enum definition
+ *
+ * please *note* that the timer values in the following section are expected
+ * in clock_t format, which is seconds multiplied by USER_HZ (generally
+ * defined as 100).
+ *
+ * @IFLA_BR_FORWARD_DELAY
+ *   The bridge forwarding delay is the time spent in LISTENING state
+ *   (before moving to LEARNING) and in LEARNING state (before moving
+ *   to FORWARDING). Only relevant if STP is enabled.
+ *
+ *   The valid values are between (2 * USER_HZ) and (30 * USER_HZ).
+ *   The default value is (15 * USER_HZ).
+ *
+ * @IFLA_BR_HELLO_TIME
+ *   The time between hello packets sent by the bridge, when it is a root
+ *   bridge or a designated bridge. Only relevant if STP is enabled.
+ *
+ *   The valid values are between (1 * USER_HZ) and (10 * USER_HZ).
+ *   The default value is (2 * USER_HZ).
+ *
+ * @IFLA_BR_MAX_AGE
+ *   The hello packet timeout, is the time until another bridge in the
+ *   spanning tree is assumed to be dead, after reception of its last hello
+ *   message. Only relevant if STP is enabled.
+ *
+ *   The valid values are between (6 * USER_HZ) and (40 * USER_HZ).
+ *   The default value is (20 * USER_HZ).
+ *
+ * @IFLA_BR_AGEING_TIME
+ *   Configure the bridge's FDB entries aging time. It is the time a MAC
+ *   address will be kept in the FDB after a packet has been received from
+ *   that address. After this time has passed, entries are cleaned up.
+ *   Allow values outside the 802.1 standard specification for special cases:
+ *
+ *     * 0 - entry never ages (all permanent)
+ *     * 1 - entry disappears (no persistence)
+ *
+ *   The default value is (300 * USER_HZ).
+ *
+ * @IFLA_BR_STP_STATE
+ *   Turn spanning tree protocol on (*IFLA_BR_STP_STATE* > 0) or off
+ *   (*IFLA_BR_STP_STATE* == 0) for this bridge.
+ *
+ *   The default value is 0 (disabled).
+ *
+ * @IFLA_BR_PRIORITY
+ *   set this bridge's spanning tree priority, used during STP root bridge
+ *   election.
+ *
+ *   The valid values are between 0 and 65535.
+ *
+ * @IFLA_BR_VLAN_FILTERING
+ *   Turn VLAN filtering on (*IFLA_BR_VLAN_FILTERING* > 0) or off
+ *   (*IFLA_BR_VLAN_FILTERING* == 0). When disabled, the bridge will not
+ *   consider the VLAN tag when handling packets.
+ *
+ *   The default value is 0 (disabled).
+ *
+ * @IFLA_BR_VLAN_PROTOCOL
+ *   Set the protocol used for VLAN filtering.
+ *
+ *   The valid values are 0x8100(802.1Q) or 0x88A8(802.1AD). The default value
+ *   is 0x8100(802.1Q).
+ *
+ * @IFLA_BR_GROUP_FWD_MASK
+ *   The group forward mask. This is the bitmask that is applied to
+ *   decide whether to forward incoming frames destined to link-local
+ *   addresses. The addresses of the form is 01:80:C2:00:00:0X, which
+ *   means the bridge does not forward any link-local frames coming on
+ *   this port).
+ *
+ *   The default value is 0.
+ *
+ * @IFLA_BR_ROOT_ID
+ *   The bridge root id, read only.
+ *
+ * @IFLA_BR_BRIDGE_ID
+ *   The bridge id, read only.
+ *
+ * @IFLA_BR_ROOT_PORT
+ *   The bridge root port, read only.
+ *
+ * @IFLA_BR_ROOT_PATH_COST
+ *   The bridge root path cost, read only.
+ *
+ * @IFLA_BR_TOPOLOGY_CHANGE
+ *   The bridge topology change, read only.
+ *
+ * @IFLA_BR_TOPOLOGY_CHANGE_DETECTED
+ *   The bridge topology change detected, read only.
+ *
+ * @IFLA_BR_HELLO_TIMER
+ *   The bridge hello timer, read only.
+ *
+ * @IFLA_BR_TCN_TIMER
+ *   The bridge tcn timer, read only.
+ *
+ * @IFLA_BR_TOPOLOGY_CHANGE_TIMER
+ *   The bridge topology change timer, read only.
+ *
+ * @IFLA_BR_GC_TIMER
+ *   The bridge gc timer, read only.
+ *
+ * @IFLA_BR_GROUP_ADDR
+ *   set the MAC address of the multicast group this bridge uses for STP.
+ *   The address must be a link-local address in standard Ethernet MAC address
+ *   format. It is an address of the form 01:80:C2:00:00:0X, with X in [0, 4..f].
+ *
+ *   The default value is 0.
+ *
+ * @IFLA_BR_FDB_FLUSH
+ *   Flush bridge's fdb dynamic entries.
+ *
+ * @IFLA_BR_MCAST_ROUTER
+ *   Set bridge's multicast router if IGMP snooping is enabled.
+ *   The valid values are:
+ *
+ *     * 0 - disabled.
+ *     * 1 - automatic (queried).
+ *     * 2 - permanently enabled.
+ *
+ *   The default value is 1.
+ *
+ * @IFLA_BR_MCAST_SNOOPING
+ *   Turn multicast snooping on (*IFLA_BR_MCAST_SNOOPING* > 0) or off
+ *   (*IFLA_BR_MCAST_SNOOPING* == 0).
+ *
+ *   The default value is 1.
+ *
+ * @IFLA_BR_MCAST_QUERY_USE_IFADDR
+ *   whether to use the bridge's own IP address as source address for IGMP
+ *   queries (*IFLA_BR_MCAST_QUERY_USE_IFADDR* > 0) or the default of 0.0.0.0
+ *   (*IFLA_BR_MCAST_QUERY_USE_IFADDR* == 0).
+ *
+ *   The default value is 0.
+ *
+ * @IFLA_BR_MCAST_QUERIER
+ *   Enable (*IFLA_BR_MULTICAST_QUERIER* > 0) or disable
+ *   (*IFLA_BR_MULTICAST_QUERIER* == 0) IGMP querier, ie sending of multicast
+ *   queries by the bridge.
+ *
+ *   The default value is 0 (disabled).
+ *
+ * @IFLA_BR_MCAST_HASH_ELASTICITY
+ *   Set multicast database hash elasticity, It is the maximum chain length in
+ *   the multicast hash table. This attribute is *deprecated* and the value
+ *   is always 16.
+ *
+ * @IFLA_BR_MCAST_HASH_MAX
+ *   Set maximum size of the multicast hash table
+ *
+ *   The default value is 4096, the value must be a power of 2.
+ *
+ * @IFLA_BR_MCAST_LAST_MEMBER_CNT
+ *   The Last Member Query Count is the number of Group-Specific Queries
+ *   sent before the router assumes there are no local members. The Last
+ *   Member Query Count is also the number of Group-and-Source-Specific
+ *   Queries sent before the router assumes there are no listeners for a
+ *   particular source.
+ *
+ *   The default value is 2.
+ *
+ * @IFLA_BR_MCAST_STARTUP_QUERY_CNT
+ *   The Startup Query Count is the number of Queries sent out on startup,
+ *   separated by the Startup Query Interval.
+ *
+ *   The default value is 2.
+ *
+ * @IFLA_BR_MCAST_LAST_MEMBER_INTVL
+ *   The Last Member Query Interval is the Max Response Time inserted into
+ *   Group-Specific Queries sent in response to Leave Group messages, and
+ *   is also the amount of time between Group-Specific Query messages.
+ *
+ *   The default value is (1 * USER_HZ).
+ *
+ * @IFLA_BR_MCAST_MEMBERSHIP_INTVL
+ *   The interval after which the bridge will leave a group, if no membership
+ *   reports for this group are received.
+ *
+ *   The default value is (260 * USER_HZ).
+ *
+ * @IFLA_BR_MCAST_QUERIER_INTVL
+ *   The interval between queries sent by other routers. if no queries are
+ *   seen after this delay has passed, the bridge will start to send its own
+ *   queries (as if **IFLA_BR_MCAST_QUERIER_INTVL** was enabled).
+ *
+ *   The default value is (255 * USER_HZ).
+ *
+ * @IFLA_BR_MCAST_QUERY_INTVL
+ *   The Query Interval is the interval between General Queries sent by
+ *   the Querier.
+ *
+ *   The default value is (125 * USER_HZ). The minimum value is (1 * USER_HZ).
+ *
+ * @IFLA_BR_MCAST_QUERY_RESPONSE_INTVL
+ *   The Max Response Time used to calculate the Max Resp Code inserted
+ *   into the periodic General Queries.
+ *
+ *   The default value is (10 * USER_HZ).
+ *
+ * @IFLA_BR_MCAST_STARTUP_QUERY_INTVL
+ *   The interval between queries in the startup phase.
+ *
+ *   The default value is (125 * USER_HZ) / 4. The minimum value is (1 * USER_HZ).
+ *
+ * @IFLA_BR_NF_CALL_IPTABLES
+ *   Enable (*NF_CALL_IPTABLES* > 0) or disable (*NF_CALL_IPTABLES* == 0)
+ *   iptables hooks on the bridge.
+ *
+ *   The default value is 0 (disabled).
+ *
+ * @IFLA_BR_NF_CALL_IP6TABLES
+ *   Enable (*NF_CALL_IP6TABLES* > 0) or disable (*NF_CALL_IP6TABLES* == 0)
+ *   ip6tables hooks on the bridge.
+ *
+ *   The default value is 0 (disabled).
+ *
+ * @IFLA_BR_NF_CALL_ARPTABLES
+ *   Enable (*NF_CALL_ARPTABLES* > 0) or disable (*NF_CALL_ARPTABLES* == 0)
+ *   arptables hooks on the bridge.
+ *
+ *   The default value is 0 (disabled).
+ *
+ * @IFLA_BR_VLAN_DEFAULT_PVID
+ *   The default PVID (native/untagged VLAN ID) for this bridge.
+ *
+ *   The default value is 1.
+ *
+ * @IFLA_BR_PAD
+ *   Bridge attribute padding type for netlink message.
+ *
+ * @IFLA_BR_VLAN_STATS_ENABLED
+ *   Enable (*IFLA_BR_VLAN_STATS_ENABLED* == 1) or disable
+ *   (*IFLA_BR_VLAN_STATS_ENABLED* == 0) per-VLAN stats accounting.
+ *
+ *   The default value is 0 (disabled).
+ *
+ * @IFLA_BR_MCAST_STATS_ENABLED
+ *   Enable (*IFLA_BR_MCAST_STATS_ENABLED* > 0) or disable
+ *   (*IFLA_BR_MCAST_STATS_ENABLED* == 0) multicast (IGMP/MLD) stats
+ *   accounting.
+ *
+ *   The default value is 0 (disabled).
+ *
+ * @IFLA_BR_MCAST_IGMP_VERSION
+ *   Set the IGMP version.
+ *
+ *   The valid values are 2 and 3. The default value is 2.
+ *
+ * @IFLA_BR_MCAST_MLD_VERSION
+ *   Set the MLD version.
+ *
+ *   The valid values are 1 and 2. The default value is 1.
+ *
+ * @IFLA_BR_VLAN_STATS_PER_PORT
+ *   Enable (*IFLA_BR_VLAN_STATS_PER_PORT* == 1) or disable
+ *   (*IFLA_BR_VLAN_STATS_PER_PORT* == 0) per-VLAN per-port stats accounting.
+ *   Can be changed only when there are no port VLANs configured.
+ *
+ *   The default value is 0 (disabled).
+ *
+ * @IFLA_BR_MULTI_BOOLOPT
+ *   The multi_boolopt is used to control new boolean options to avoid adding
+ *   new netlink attributes.
+ *
+ * @IFLA_BR_MCAST_QUERIER_STATE
+ *   Bridge mcast querier states, read only.
+ *
+ * @IFLA_BR_FDB_N_LEARNED
+ *   The number of dynamically learned FDB entries for the current bridge,
+ *   read only.
+ *
+ * @IFLA_BR_FDB_MAX_LEARNED
+ *   Set the number of max dynamically learned FDB entries for the current
+ *   bridge.
+ */
 enum {
 	IFLA_BR_UNSPEC,
 	IFLA_BR_FORWARD_DELAY,
-- 
2.41.0

Re: [PATCH net-next 01/10] net: bridge: add document for IFLA_BR enum

[Jakub Kicinski]

On Fri, 17 Nov 2023 17:31:36 +0800 Hangbin Liu wrote:
> Add document for IFLA_BR enum so we can use it in
> Documentation/networking/bridge.rst.

Did you consider writing a YAML spec instead?

It's unlikely to be usable today with YNL due to all the classic
netlink vs genetlink differences, but Breno is working on rendering 
the specs in documentation:

https://lore.kernel.org/all/20231113202936.242308-1-leitao@debian.org/

so in terms of just documenting attributes it may be good enough.
It may possibly be nice to have that documentation folder as "one 
stop shop" for all of netlink?

Absolutely no strong preference on my side, just wanted to make
sure you're aware of that work.

Re: [PATCH net-next 01/10] net: bridge: add document for IFLA_BR enum

[Hangbin Liu]

On Sat, Nov 18, 2023 at 09:45:25AM -0800, Jakub Kicinski wrote:
> On Fri, 17 Nov 2023 17:31:36 +0800 Hangbin Liu wrote:
> > Add document for IFLA_BR enum so we can use it in
> > Documentation/networking/bridge.rst.
> 
> Did you consider writing a YAML spec instead?
> 
> It's unlikely to be usable today with YNL due to all the classic
> netlink vs genetlink differences, but Breno is working on rendering 
> the specs in documentation:
> 
> https://lore.kernel.org/all/20231113202936.242308-1-leitao@debian.org/
> 
> so in terms of just documenting attributes it may be good enough.
> It may possibly be nice to have that documentation folder as "one 
> stop shop" for all of netlink?

Thanks for this info. Will the YAML spec be build by the document team?
I'd prefer all the doc shows in https://www.kernel.org/doc/html/latest/
so users could find the doc easily.

It would be good if there is an example in Documentation/netlink/specs/ (when
the patch applied) so I can take as a reference :)

Thanks
Hangbin
> 
> Absolutely no strong preference on my side, just wanted to make
> sure you're aware of that work.

Re: [PATCH net-next 01/10] net: bridge: add document for IFLA_BR enum

[Jakub Kicinski]

On Tue, 21 Nov 2023 11:28:30 +0800 Hangbin Liu wrote:
> Thanks for this info. Will the YAML spec be build by the document team?
> I'd prefer all the doc shows in https://www.kernel.org/doc/html/latest/
> so users could find the doc easily.

That's the plan, it will render under ${base}/networking/netlink_spec/

> It would be good if there is an example in Documentation/netlink/specs/ (when
> the patch applied) so I can take as a reference :)

All the operations, attributes etc in the spec accept a "doc" property.
The html output is just a rendering of those doc strings.
So the existing specs are already kind of examples, although they don't
have doc strings in very many places so the output looks a bit empty :(

Re: [PATCH net-next 01/10] net: bridge: add document for IFLA_BR enum

[Hangbin Liu]

On Tue, Nov 21, 2023 at 08:21:27AM -0800, Jakub Kicinski wrote:
> On Tue, 21 Nov 2023 11:28:30 +0800 Hangbin Liu wrote:
> > Thanks for this info. Will the YAML spec be build by the document team?
> > I'd prefer all the doc shows in https://www.kernel.org/doc/html/latest/
> > so users could find the doc easily.
> 
> That's the plan, it will render under ${base}/networking/netlink_spec/
> 
> > It would be good if there is an example in Documentation/netlink/specs/ (when
> > the patch applied) so I can take as a reference :)
> 
> All the operations, attributes etc in the spec accept a "doc" property.
> The html output is just a rendering of those doc strings.
> So the existing specs are already kind of examples, although they don't
> have doc strings in very many places so the output looks a bit empty :(

Thanks, I will investigate how to convert the bridge yaml. But next week
I will be in vacation. So I may post another patch after vacation.

Regards
Hangbin

Re: [PATCH net-next 01/10] net: bridge: add document for IFLA_BR enum

[Vladimir Oltean]

On Fri, Nov 17, 2023 at 05:31:36PM +0800, Hangbin Liu wrote:
> + * @IFLA_BR_MAX_AGE
> + *   The hello packet timeout, is the time until another bridge in the

No comma between subject and predicate.

> + *   spanning tree is assumed to be dead, after reception of its last hello
> + *   message. Only relevant if STP is enabled.
> + *
> + *   The valid values are between (6 * USER_HZ) and (40 * USER_HZ).
> + *   The default value is (20 * USER_HZ).
> + *
> + * @IFLA_BR_GROUP_FWD_MASK
> + *   The group forward mask. This is the bitmask that is applied to
> + *   decide whether to forward incoming frames destined to link-local
> + *   addresses. The addresses of the form is 01:80:C2:00:00:0X, which
> + *   means the bridge does not forward any link-local frames coming on
> + *   this port).
> + *
> + *   The default value is 0.

I'm confused by this description, I believe some of the wording is
misplaced. Maybe:

   The group forwarding mask. This is the bitmask that is applied to
   decide whether to forward incoming frames destined to link-local
   addresses (of the form 01:80:C2:00:00:0X).

   The default value is 0, which means the bridge does not forward any
   link-local frames coming on this port.

> + * @IFLA_BR_VLAN_DEFAULT_PVID
> + *   The default PVID (native/untagged VLAN ID) for this bridge.

I don't think that "native VLAN" is a good description of this.
The native VLAN should be the only egress-untagged VLAN of a port.

I would say "VLAN ID applied to untagged and priority-tagged incoming
packets".

> + *
> + *   The default value is 1.

I would also mention that the special value of 0 makes all ports of
this bridge not have a PVID by default, which means that they will
not accept VLAN-untagged traffic.

Re: [PATCH net-next 01/10] net: bridge: add document for IFLA_BR enum

[Andrew Lunn]

On Sun, Nov 19, 2023 at 06:46:25PM +0200, Vladimir Oltean wrote:
> On Fri, Nov 17, 2023 at 05:31:36PM +0800, Hangbin Liu wrote:
> > + * @IFLA_BR_MAX_AGE
> > + *   The hello packet timeout, is the time until another bridge in the
> 
> No comma between subject and predicate.
> 
> > + *   spanning tree is assumed to be dead, after reception of its last hello
> > + *   message. Only relevant if STP is enabled.
> > + *
> > + *   The valid values are between (6 * USER_HZ) and (40 * USER_HZ).
> > + *   The default value is (20 * USER_HZ).
> > + *
> > + * @IFLA_BR_GROUP_FWD_MASK
> > + *   The group forward mask. This is the bitmask that is applied to
> > + *   decide whether to forward incoming frames destined to link-local
> > + *   addresses. The addresses of the form is 01:80:C2:00:00:0X, which
> > + *   means the bridge does not forward any link-local frames coming on
> > + *   this port).
> > + *
> > + *   The default value is 0.

Where was the default value of 0 derived from?

br_handle_frame() seems to handle 01-80-C2-00-00-00 using is used for
BPDUs. 01-80-C2-00-00-01 is explicitly dropped, since its Pause, which
i doubt you want to forward. LLDP has some level of processing.

Should the default value reflect this?

       Andrew

Re: [PATCH net-next 01/10] net: bridge: add document for IFLA_BR enum

[Hangbin Liu]

On Sun, Nov 19, 2023 at 07:21:25PM +0100, Andrew Lunn wrote:
> > > + * @IFLA_BR_GROUP_FWD_MASK
> > > + *   The group forward mask. This is the bitmask that is applied to
> > > + *   decide whether to forward incoming frames destined to link-local
> > > + *   addresses. The addresses of the form is 01:80:C2:00:00:0X, which
> > > + *   means the bridge does not forward any link-local frames coming on
> > > + *   this port).
> > > + *
> > > + *   The default value is 0.
> 
> Where was the default value of 0 derived from?

I doc it as 0 because I saw in br_dev_setup()

        br->stp_enabled = BR_NO_STP;
        br->group_fwd_mask = BR_GROUPFWD_DEFAULT;
        br->group_fwd_mask_required = BR_GROUPFWD_DEFAULT;

and #define BR_GROUPFWD_DEFAULT     0

Thanks
Hangbin
> 
> br_handle_frame() seems to handle 01-80-C2-00-00-00 using is used for
> BPDUs. 01-80-C2-00-00-01 is explicitly dropped, since its Pause, which
> i doubt you want to forward. LLDP has some level of processing.
> 
> Should the default value reflect this?
> 
>        Andrew

Re: [PATCH net-next 01/10] net: bridge: add document for IFLA_BR enum

[Hangbin Liu]

On Sun, Nov 19, 2023 at 06:46:25PM +0200, Vladimir Oltean wrote:
> On Fri, Nov 17, 2023 at 05:31:36PM +0800, Hangbin Liu wrote:
> > + * @IFLA_BR_MAX_AGE
> > + *   The hello packet timeout, is the time until another bridge in the
> 
> No comma between subject and predicate.
> 
> > + *   spanning tree is assumed to be dead, after reception of its last hello
> > + *   message. Only relevant if STP is enabled.
> > + *
> > + *   The valid values are between (6 * USER_HZ) and (40 * USER_HZ).
> > + *   The default value is (20 * USER_HZ).
> > + *
> > + * @IFLA_BR_GROUP_FWD_MASK
> > + *   The group forward mask. This is the bitmask that is applied to
> > + *   decide whether to forward incoming frames destined to link-local
> > + *   addresses. The addresses of the form is 01:80:C2:00:00:0X, which
> > + *   means the bridge does not forward any link-local frames coming on
> > + *   this port).
> > + *
> > + *   The default value is 0.
> 
> I'm confused by this description, I believe some of the wording is
> misplaced. Maybe:
> 
>    The group forwarding mask. This is the bitmask that is applied to
>    decide whether to forward incoming frames destined to link-local
>    addresses (of the form 01:80:C2:00:00:0X).
> 
>    The default value is 0, which means the bridge does not forward any
>    link-local frames coming on this port.
> 
> > + * @IFLA_BR_VLAN_DEFAULT_PVID
> > + *   The default PVID (native/untagged VLAN ID) for this bridge.
> 
> I don't think that "native VLAN" is a good description of this.
> The native VLAN should be the only egress-untagged VLAN of a port.
> 
> I would say "VLAN ID applied to untagged and priority-tagged incoming
> packets".
> 
> > + *
> > + *   The default value is 1.
> 
> I would also mention that the special value of 0 makes all ports of
> this bridge not have a PVID by default, which means that they will
> not accept VLAN-untagged traffic.

Thanks for the comments. I will update it in next version.

Hangbin

[PATCH net-next 02/10] net: bridge: add document for IFLA_BRPORT enum

[Hangbin Liu]

Add document for IFLA_BRPORT enum so we can use it in
Documentation/networking/bridge.rst.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 include/uapi/linux/if_link.h | 222 +++++++++++++++++++++++++++++++++++
 1 file changed, 222 insertions(+)

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 8debf1c62a6d..1e7b4473255d 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -800,11 +800,233 @@ struct ifla_bridge_id {
 	__u8	addr[6]; /* ETH_ALEN */
 };
 
+/**
+ * DOC: Bridge mode enum definition
+ *
+ * @BRIDGE_MODE_HAIRPIN
+ *   Controls whether traffic may be send back out of the port on which it
+ *   was received. This option is also called reflective relay mode, and is
+ *   used to support basic VEPA (Virtual Ethernet Port Aggregator)
+ *   capabilities. By default, this flag is turned off and the bridge will
+ *   not forward traffic back out of the receiving port.
+ */
 enum {
 	BRIDGE_MODE_UNSPEC,
 	BRIDGE_MODE_HAIRPIN,
 };
 
+/**
+ * DOC: Bridge port enum definition
+ *
+ * @IFLA_BRPORT_STATE
+ *   The operation state of the port. Here are the valid values.
+ *
+ *     * 0 - port is in STP *DISABLED* state. Make this port completely
+ *       inactive for STP. This is also called BPDU filter and could be used
+ *       to disable STP on an untrusted port, like a leaf virtual device.
+ *       The traffic forwarding is also stopped on this port.
+ *     * 1 - port is in STP *LISTENING* state. Only valid if STP is enabled
+ *       on the bridge. In this state the port listens for STP BPDUs and
+ *       drops all other traffic frames.
+ *     * 2 - port is in STP *LEARNING* state. Only valid if STP is enabled on
+ *       the bridge. In this state the port will accept traffic only for the
+ *       purpose of updating MAC address tables.
+ *     * 3 - port is in STP *FORWARDING* state. Port is fully active.
+ *     * 4 - port is in STP *BLOCKING* state. Only valid if STP is enabled on
+ *       the bridge. This state is used during the STP election process.
+ *       In this state, port will only process STP BPDUs.
+ *
+ * @IFLA_BRPORT_PRIORITY
+ *   The STP port priority. The valid values are between 0 and 255.
+ *
+ * @IFLA_BRPORT_COST
+ *   The STP path cost of the port. The valid values are between 1 and 65535.
+ *
+ * @IFLA_BRPORT_MODE
+ *   Set the bridge port mode. See *BRIDGE_MODE_HAIRPIN* for more details.
+ *
+ * @IFLA_BRPORT_GUARD
+ *   Controls whether STP BPDUs will be processed by the bridge port. By
+ *   default, the flag is turned off to allow BPDU processing. Turning this
+ *   flag on will disable the bridge port if a STP BPDU packet is received.
+ *
+ *   If the bridge has Spanning Tree enabled, hostile devices on the network
+ *   may send BPDU on a port and cause network failure. Setting *guard on*
+ *   will detect and stop this by disabling the port. The port will be
+ *   restarted if the link is brought down, or removed and reattached.
+ *
+ * @IFLA_BRPORT_PROTECT
+ *   Controls whether a given port is allowed to become a root port or not.
+ *   Only used when STP is enabled on the bridge. By default the flag is off.
+ *
+ *   This feature is also called root port guard. If BPDU is received from a
+ *   leaf (edge) port, it should not be elected as root port. This could
+ *   be used if using STP on a bridge and the downstream bridges are not fully
+ *   trusted; this prevents a hostile guest from rerouting traffic.
+ *
+ * @IFLA_BRPORT_FAST_LEAVE
+ *   This flag allows the bridge to immediately stop multicast traffic
+ *   forwarding on a port that receives an IGMP Leave message. It is only used
+ *   when IGMP snooping is enabled on the bridge. By default the flag is off.
+ *
+ * @IFLA_BRPORT_LEARNING
+ *   Controls whether a given port will learn *source* MAC addresses from
+ *   received traffic or not. By default this flag is on.
+ *
+ * @IFLA_BRPORT_UNICAST_FLOOD
+ *   Controls whether unicast traffic for which there is no FDB entry will
+ *   be flooded towards this port. By default this flag is on.
+ *
+ * @IFLA_BRPORT_PROXYARP
+ *   Enable proxy ARP on this port.
+ *
+ * @IFLA_BRPORT_LEARNING_SYNC
+ *   Controls whether a given port will sync MAC addresses learned on device
+ *   port to bridge FDB.
+ *
+ * @IFLA_BRPORT_PROXYARP_WIFI
+ *   Enable proxy ARP on this port which meets extended requirements by
+ *   IEEE 802.11 and Hotspot 2.0 specifications.
+ *
+ * @IFLA_BRPORT_ROOT_ID
+ *
+ * @IFLA_BRPORT_BRIDGE_ID
+ *
+ * @IFLA_BRPORT_DESIGNATED_PORT
+ *
+ * @IFLA_BRPORT_DESIGNATED_COST
+ *
+ * @IFLA_BRPORT_ID
+ *
+ * @IFLA_BRPORT_NO
+ *
+ * @IFLA_BRPORT_TOPOLOGY_CHANGE_ACK
+ *
+ * @IFLA_BRPORT_CONFIG_PENDING
+ *
+ * @IFLA_BRPORT_MESSAGE_AGE_TIMER
+ *
+ * @IFLA_BRPORT_FORWARD_DELAY_TIMER
+ *
+ * @IFLA_BRPORT_HOLD_TIMER
+ *
+ * @IFLA_BRPORT_FLUSH
+ *   Flush bridge ports' fdb dynamic entries.
+ *
+ * @IFLA_BRPORT_MULTICAST_ROUTER
+ *   Configure the port's multicast router presence. A port with
+ *   a multicast router will receive all multicast traffic.
+ *   The valid values are:
+ *
+ *     * 0 disable multicast routers on this port
+ *     * 1 let the system detect the presence of routers (default)
+ *     * 2 permanently enable multicast traffic forwarding on this port
+ *     * 3 enable multicast routers temporarily on this port, not depending
+ *         on incoming queries.
+ *
+ * @IFLA_BRPORT_PAD
+ *
+ * @IFLA_BRPORT_MCAST_FLOOD
+ *   Controls whether a given port will flood multicast traffic for which
+ *   there is no MDB entry. By default this flag is on.
+ *
+ * @IFLA_BRPORT_MCAST_TO_UCAST
+ *   Controls whether a given port will replicate packets using unicast
+ *   instead of multicast. By default this flag is off.
+ *
+ *   This is done by copying the packet per host and changing the multicast
+ *   destination MAC to a unicast one accordingly.
+ *
+ *   *mcast_to_unicast* works on top of the multicast snooping feature of the
+ *   bridge. Which means unicast copies are only delivered to hosts which
+ *   are interested in unicast and signaled this via IGMP/MLD reports previously.
+ *
+ *   This feature is intended for interface types which have a more reliable
+ *   and/or efficient way to deliver unicast packets than broadcast ones
+ *   (e.g. WiFi).
+ *
+ *   However, it should only be enabled on interfaces where no IGMPv2/MLDv1
+ *   report suppression takes place. IGMP/MLD report suppression issue is
+ *   usually overcome by the network daemon (supplicant) enabling AP isolation
+ *   and by that separating all STAs.
+ *
+ *   Delivery of STA-to-STA IP multicast is made possible again by enabling
+ *   and utilizing the bridge hairpin mode, which considers the incoming port
+ *   as a potential outgoing port, too (see *BRIDGE_MODE_HAIRPIN* option).
+ *   Hairpin mode is performed after multicast snooping, therefore leading
+ *   to only deliver reports to STAs running a multicast router.
+ *
+ * @IFLA_BRPORT_VLAN_TUNNEL
+ *   Controls whether vlan to tunnel mapping is enabled on the port.
+ *   By default this flag is off.
+ *
+ * @IFLA_BRPORT_BCAST_FLOOD
+ *   Controls flooding of broadcast traffic on the given port. By default
+ *   this flag is on.
+ *
+ * @IFLA_BRPORT_GROUP_FWD_MASK
+ *   Set the group forward mask. This is a bitmask that is applied to
+ *   decide whether to forward incoming frames destined to link-local
+ *   addresses. The addresses of the form are 01:80:C2:00:00:0X (defaults
+ *   to 0, which means the bridge does not forward any link-local frames
+ *   coming on this port).
+ *
+ * @IFLA_BRPORT_NEIGH_SUPPRESS
+ *   Controls whether neighbor discovery (arp and nd) proxy and suppression
+ *   is enabled on the port. By default this flag is off.
+ *
+ * @IFLA_BRPORT_ISOLATED
+ *   Controls whether a given port will be isolated, which means it will be
+ *   able to communicate with non-isolated ports only. By default this
+ *   flag is off.
+ *
+ * @IFLA_BRPORT_BACKUP_PORT
+ *   Set a backup port. If the port loses carrier all traffic will be
+ *   redirected to the configured backup port. Set the value to 0 to disable
+ *   it.
+ *
+ * @IFLA_BRPORT_MRP_RING_OPEN
+ *
+ * @IFLA_BRPORT_MRP_IN_OPEN
+ *
+ * @IFLA_BRPORT_MCAST_EHT_HOSTS_LIMIT
+ *   The number of per-port EHT hosts limit. The default value is 512.
+ *   Setting to 0 is not allowed.
+ *
+ * @IFLA_BRPORT_MCAST_EHT_HOSTS_CNT
+ *   The current number of tracked hosts, read only.
+ *
+ * @IFLA_BRPORT_LOCKED
+ *   Controls whether a port will be locked, meaning that hosts behind the
+ *   port will not be able to communicate through the port unless an FDB
+ *   entry with the unit's MAC address is in the FDB. The common use case is
+ *   that hosts are allowed access through authentication with the IEEE 802.1X
+ *   protocol or based on whitelists. By default this flag is off.
+ *
+ * @IFLA_BRPORT_MAB
+ *
+ * @IFLA_BRPORT_MCAST_N_GROUPS
+ *
+ * @IFLA_BRPORT_MCAST_MAX_GROUPS
+ *   Sets the maximum number of MDB entries that can be registered for a
+ *   given port. Attempts to register more MDB entries at the port than this
+ *   limit allows will be rejected, whether they are done through netlink
+ *   (e.g. the bridge tool), or IGMP or MLD membership reports. Setting a
+ *   limit of 0 disables the limit. The default value is 0.
+ *
+ * @IFLA_BRPORT_NEIGH_VLAN_SUPPRESS
+ *   Controls whether neighbor discovery (arp and nd) proxy and suppression is
+ *   enabled for a given port. By default this flag is off.
+ *
+ *   Note that this option only takes effect when *IFLA_BRPORT_NEIGH_SUPPRESS*
+ *   is enabled for a given port.
+ *
+ * @IFLA_BRPORT_BACKUP_NHID
+ *   The FDB nexthop object ID to attach to packets being redirected to a
+ *   backup port that has VLAN tunnel mapping enabled (via the
+ *   *IFLA_BRPORT_VLAN_TUNNEL* option). Setting a value of 0 (default) has
+ *   the effect of not attaching any ID.
+ */
 enum {
 	IFLA_BRPORT_UNSPEC,
 	IFLA_BRPORT_STATE,	/* Spanning tree state     */
-- 
2.41.0

Re: [PATCH net-next 02/10] net: bridge: add document for IFLA_BRPORT enum

[Vladimir Oltean]

On Fri, Nov 17, 2023 at 05:31:37PM +0800, Hangbin Liu wrote:
> + * @IFLA_BRPORT_LEARNING
> + *   Controls whether a given port will learn *source* MAC addresses from
> + *   received traffic or not. By default this flag is on.

Also controls whether dynamic FDB entries (which can also be added by
software) will be refreshed by incoming traffic.

This is subtle but important in certain use cases (below).

> + * @IFLA_BRPORT_LOCKED
> + *   Controls whether a port will be locked, meaning that hosts behind the
> + *   port will not be able to communicate through the port unless an FDB
> + *   entry with the unit's MAC address is in the FDB. The common use case is
> + *   that hosts are allowed access through authentication with the IEEE 802.1X
> + *   protocol or based on whitelists. By default this flag is off.

Here seems like a good place to add this warning:

Secure 802.1X deployments should always use the BR_BOOLOPT_NO_LL_LEARN
flag, to not permit the bridge to populate its FDB based on link-local
(EAPOL) traffic received on the port.

> + *
> + * @IFLA_BRPORT_MAB

Controls whether a port will use MAC Authentication Bypass (MAB), a
technique through which select MAC addresses may be allowed on a locked
port, without using 802.1X authentication. Packets with an unknown source
MAC address generate a "locked" FDB entry on the incoming bridge port.
The common use case is for user space to react to these bridge FDB
notifications and optionally replace the locked FDB entry with a normal
one, allowing traffic to pass for whitelisted MAC addresses.

Setting this flag also requires IFLA_BRPORT_LOCKED and IFLA_BRPORT_LEARNING.
IFLA_BRPORT_LOCKED ensures that unauthorized data packets are dropped,
and IFLA_BRPORT_LEARNING allows the dynamic FDB entries installed by
user space (as replacements for the locked FDB entries) to be refreshed
and/or aged out.

(source: https://lore.kernel.org/netdev/20221018165619.134535-11-netdev@kapio-technology.com/)

Re: [PATCH net-next 02/10] net: bridge: add document for IFLA_BRPORT enum

[Hangbin Liu]

On Mon, Nov 20, 2023 at 01:31:27PM +0200, Vladimir Oltean wrote:
> On Fri, Nov 17, 2023 at 05:31:37PM +0800, Hangbin Liu wrote:
> > + * @IFLA_BRPORT_LEARNING
> > + *   Controls whether a given port will learn *source* MAC addresses from
> > + *   received traffic or not. By default this flag is on.
> 
> Also controls whether dynamic FDB entries (which can also be added by
> software) will be refreshed by incoming traffic.
> 
> This is subtle but important in certain use cases (below).
> 
> > + * @IFLA_BRPORT_LOCKED
> > + *   Controls whether a port will be locked, meaning that hosts behind the
> > + *   port will not be able to communicate through the port unless an FDB
> > + *   entry with the unit's MAC address is in the FDB. The common use case is
> > + *   that hosts are allowed access through authentication with the IEEE 802.1X
> > + *   protocol or based on whitelists. By default this flag is off.
> 
> Here seems like a good place to add this warning:
> 
> Secure 802.1X deployments should always use the BR_BOOLOPT_NO_LL_LEARN
> flag, to not permit the bridge to populate its FDB based on link-local
> (EAPOL) traffic received on the port.
> 
> > + *
> > + * @IFLA_BRPORT_MAB
> 
> Controls whether a port will use MAC Authentication Bypass (MAB), a
> technique through which select MAC addresses may be allowed on a locked
> port, without using 802.1X authentication. Packets with an unknown source
> MAC address generate a "locked" FDB entry on the incoming bridge port.
> The common use case is for user space to react to these bridge FDB
> notifications and optionally replace the locked FDB entry with a normal
> one, allowing traffic to pass for whitelisted MAC addresses.
> 
> Setting this flag also requires IFLA_BRPORT_LOCKED and IFLA_BRPORT_LEARNING.
> IFLA_BRPORT_LOCKED ensures that unauthorized data packets are dropped,
> and IFLA_BRPORT_LEARNING allows the dynamic FDB entries installed by
> user space (as replacements for the locked FDB entries) to be refreshed
> and/or aged out.
> 
> (source: https://lore.kernel.org/netdev/20221018165619.134535-11-netdev@kapio-technology.com/)

Tanks for the doc, I will update the patch.

Hangbin

[PATCH net-next 03/10] net: bridge: add document for bridge sysfs attribute

[Hangbin Liu]

Although the sysfs interface is deprecated and should not be extended
if new options are added. There are still users and admins use this
interface to config bridge options. It would help users to know what
the meaning of each field. Add correspond netlink enums (as we have
document for them) for bridge sysfs attributes, so we can use it in
Documentation/networking/bridge.rst.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 net/bridge/br_sysfs_br.c | 93 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)

diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
index ea733542244c..bd9c9b2a7859 100644
--- a/net/bridge/br_sysfs_br.c
+++ b/net/bridge/br_sysfs_br.c
@@ -933,6 +933,99 @@ static ssize_t vlan_stats_per_port_store(struct device *d,
 static DEVICE_ATTR_RW(vlan_stats_per_port);
 #endif
 
+/**
+ * DOC: Bridge sysfs attributes
+ *
+ * @forward_delay: IFLA_BR_FORWARD_DELAY
+ *
+ * @hello_time: IFLA_BR_HELLO_TIME
+ *
+ * @max_age: IFLA_BR_MAX_AGE
+ *
+ * @ageing_time: IFLA_BR_AGEING_TIME
+ *
+ * @stp_state: IFLA_BR_STP_STATE
+ *
+ * @group_fwd_mask: IFLA_BR_GROUP_FWD_MASK
+ *
+ * @priority: IFLA_BR_PRIORITY
+ *
+ * @bridge_id: IFLA_BR_BRIDGE_ID
+ *
+ * @root_id: IFLA_BR_ROOT_ID
+ *
+ * @root_path_cost: IFLA_BR_ROOT_PATH_COST
+ *
+ * @root_port: IFLA_BR_ROOT_PORT
+ *
+ * @topology_change: IFLA_BR_TOPOLOGY_CHANGE
+ *
+ * @topology_change_detected: IFLA_BR_TOPOLOGY_CHANGE_DETECTED
+ *
+ * @hello_timer: IFLA_BR_HELLO_TIMER
+ *
+ * @tcn_timer: IFLA_BR_TCN_TIMER
+ *
+ * @topology_change_timer: IFLA_BR_TOPOLOGY_CHANGE_TIMER
+ *
+ * @gc_timer: IFLA_BR_GC_TIMER
+ *
+ * @group_addr: IFLA_BR_GROUP_ADDR
+ *
+ * @flush: IFLA_BR_FDB_FLUSH
+ *
+ * @no_linklocal_learn: BR_BOOLOPT_NO_LL_LEARN
+ *
+ * @multicast_router: IFLA_BR_MCAST_ROUTER
+ *
+ * @multicast_snooping: IFLA_BR_MCAST_SNOOPING
+ *
+ * @multicast_querier: IFLA_BR_MCAST_QUERIER
+ *
+ * @multicast_query_use_ifaddr: IFLA_BR_MCAST_QUERY_USE_IFADDR
+ *
+ * @hash_elasticity: IFLA_BR_MCAST_HASH_ELASTICITY
+ *
+ * @hash_max: IFLA_BR_MCAST_HASH_MAX
+ *
+ * @multicast_last_member_count: IFLA_BR_MCAST_LAST_MEMBER_CNT
+ *
+ * @multicast_startup_query_count: IFLA_BR_MCAST_STARTUP_QUERY_CNT
+ *
+ * @multicast_last_member_interval: IFLA_BR_MCAST_LAST_MEMBER_INTVL
+ *
+ * @multicast_membership_interval: IFLA_BR_MCAST_MEMBERSHIP_INTVL
+ *
+ * @multicast_querier_interval: IFLA_BR_MCAST_QUERIER_INTVL
+ *
+ * @multicast_query_interval: IFLA_BR_MCAST_QUERY_INTVL
+ *
+ * @multicast_query_response_interval: IFLA_BR_MCAST_QUERY_RESPONSE_INTVL
+ *
+ * @multicast_startup_query_interval: IFLA_BR_MCAST_STARTUP_QUERY_INTVL
+ *
+ * @multicast_stats_enabled: IFLA_BR_MCAST_STATS_ENABLED
+ *
+ * @multicast_igmp_version: IFLA_BR_MCAST_IGMP_VERSION
+ *
+ * @multicast_mld_version: IFLA_BR_MCAST_MLD_VERSION
+ *
+ * @nf_call_iptables: IFLA_BR_NF_CALL_IPTABLES
+ *
+ * @nf_call_ip6tables: IFLA_BR_NF_CALL_IP6TABLES
+ *
+ * @nf_call_arptables: IFLA_BR_NF_CALL_ARPTABLES
+ *
+ * @vlan_filtering: IFLA_BR_VLAN_FILTERING
+ *
+ * @vlan_protocol: IFLA_BR_VLAN_PROTOCOL
+ *
+ * @default_pvid: IFLA_BR_VLAN_DEFAULT_PVID
+ *
+ * @vlan_stats_enabled: IFLA_BR_VLAN_STATS_ENABLED
+ *
+ * @vlan_stats_per_port: IFLA_BR_VLAN_STATS_PER_PORT
+ */
 static struct attribute *bridge_attrs[] = {
 	&dev_attr_forward_delay.attr,
 	&dev_attr_hello_time.attr,
-- 
2.41.0

[PATCH net-next 04/10] docs: bridge: Add kAPI/uAPI fields

[Hangbin Liu]

The current bridge kernel doc is too old. It only pointed to the
linuxfoundation wiki page which lacks of the new features.

Here let's start the new bridge document and put all the bridge info
so new developers and users could catch up the last bridge status soon.

First, add kAPI/uAPI and FAQ fields. These 2 fields are only examples and
more APIs need to be added in future.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 Documentation/networking/bridge.rst | 84 +++++++++++++++++++++++++----
 net/bridge/br_private.h             |  2 +
 2 files changed, 76 insertions(+), 10 deletions(-)

diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst
index c859f3c1636e..84aae94f6598 100644
--- a/Documentation/networking/bridge.rst
+++ b/Documentation/networking/bridge.rst
@@ -4,18 +4,82 @@
 Ethernet Bridging
 =================
 
-In order to use the Ethernet bridging functionality, you'll need the
-userspace tools.
+Introduction
+============
 
-Documentation for Linux bridging is on:
-   https://wiki.linuxfoundation.org/networking/bridge
+A bridge is a way to connect multiple Ethernet segments together in a protocol
+independent way. Packets are forwarded based on Layer 2 destination Ethernet
+address, rather than IP address (like a router). Since forwarding is done
+at Layer 2, all Layer 3 protocols can pass through a bridge transparently.
 
-The bridge-utilities are maintained at:
-   git://git.kernel.org/pub/scm/linux/kernel/git/shemminger/bridge-utils.git
+Bridge kAPI
+===========
 
-Additionally, the iproute2 utilities can be used to configure
-bridge devices.
+Here are some core structures of bridge code.
 
-If you still have questions, don't hesitate to post to the mailing list 
-(more info https://lists.linux-foundation.org/mailman/listinfo/bridge).
+.. kernel-doc:: net/bridge/br_private.h
+   :identifiers: net_bridge_vlan
 
+Bridge uAPI
+===========
+
+Modern Linux bridge uAPI is accessed via Netlink interface. You can find
+below files where the bridge and bridge port netlink attributes are defined.
+
+Bridge netlink attributes
+-------------------------
+
+.. kernel-doc:: include/uapi/linux/if_link.h
+   :doc: Bridge enum definition
+
+Bridge port netlink attributes
+------------------------------
+
+.. kernel-doc:: include/uapi/linux/if_link.h
+   :doc: Bridge port enum definition
+
+Bridge sysfs
+------------
+
+All sysfs attributes are also exported via the bridge netlink API.
+You can find each attribute explanation based on the correspond netlink
+attribute.
+
+NOTE: the sysfs interface is deprecated and should not be extended if new
+options are added.
+
+.. kernel-doc:: net/bridge/br_sysfs_br.c
+   :doc: Bridge sysfs attributes
+
+FAQ
+===
+
+What does a bridge do?
+----------------------
+
+A bridge transparently forwards traffic between multiple network interfaces.
+In plain English this means that a bridge connects two or more physical
+Ethernet networks, to form one larger (logical) Ethernet network.
+
+Is it L3 protocol independent?
+------------------------------
+
+Yes. The bridge sees all frames, but it *uses* only L2 headers/information.
+As such, the bridging functionality is protocol independent, and there should
+be no trouble forwarding IPX, NetBEUI, IP, IPv6, etc.
+
+Contact Info
+============
+
+The code is currently maintained by Roopa Prabhu <roopa@nvidia.com> and
+Nikolay Aleksandrov <razor@blackwall.org>. Bridge bugs and enhancements
+are discussed on the linux-netdev mailing list netdev@vger.kernel.org and
+bridge@lists.linux-foundation.org.
+
+The list is open to anyone interested: http://vger.kernel.org/vger-lists.html#netdev
+
+External Links
+==============
+
+The old Documentation for Linux bridging is on:
+https://wiki.linuxfoundation.org/networking/bridge
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 6b7f36769d03..051ea81864ac 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -186,6 +186,7 @@ enum {
  * struct net_bridge_vlan - per-vlan entry
  *
  * @vnode: rhashtable member
+ * @tnode: rhashtable member
  * @vid: VLAN id
  * @flags: bridge vlan flags
  * @priv_flags: private (in-kernel) bridge vlan flags
@@ -196,6 +197,7 @@ enum {
  * @refcnt: if MASTER flag set, this is bumped for each port referencing it
  * @brvlan: if MASTER flag unset, this points to the global per-VLAN context
  *          for this VLAN entry
+ * @tinfo: bridge tunnel info
  * @br_mcast_ctx: if MASTER flag set, this is the global vlan multicast context
  * @port_mcast_ctx: if MASTER flag unset, this is the per-port/vlan multicast
  *                  context
-- 
2.41.0

[PATCH net-next 05/10] docs: bridge: add STP doc

[Hangbin Liu]

Add STP part for bridge document.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 Documentation/networking/bridge.rst | 85 +++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst
index 84aae94f6598..1fd339e48129 100644
--- a/Documentation/networking/bridge.rst
+++ b/Documentation/networking/bridge.rst
@@ -51,6 +51,91 @@ options are added.
 .. kernel-doc:: net/bridge/br_sysfs_br.c
    :doc: Bridge sysfs attributes
 
+STP
+===
+
+The STP (Spanning Tree Protocol) implementation in the Linux bridge driver
+is a critical feature that helps prevent loops and broadcast storms in
+Ethernet networks by identifying and disabling redundant links. In a Linux
+bridge context, STP is crucial for network stability and availability.
+
+STP is a Layer 2 protocol that operates at the Data Link Layer of the OSI
+model. It was originally developed as IEEE 802.1D and has since evolved into
+multiple versions, including Rapid Spanning Tree Protocol (RSTP) and
+`Multiple Spanning Tree Protocol (MSTP)
+<https://lore.kernel.org/netdev/20220316150857.2442916-1-tobias@waldekranz.com/>`_.
+
+Bridge Ports and STP States
+---------------------------
+
+In the context of STP, bridge ports can be in one of the following states:
+  * Blocking: The port is disabled for data traffic and only listens for
+    BPDUs (Bridge Protocol Data Units) from other devices to determine the
+    network topology.
+  * Listening: The port begins to participate in the STP process and listens
+    for BPDUs.
+  * Learning: The port continues to listen for BPDUs and begins to learn MAC
+    addresses from incoming frames but does not forward data frames.
+  * Forwarding: The port is fully operational and forwards both BPDUs and
+    data frames.
+  * Disabled: The port is administratively disabled and does not participate
+    in the STP process. The data frames forwarding are also disabled.
+
+Root Bridge and Convergence
+---------------------------
+
+In the context of networking and Ethernet bridging in Linux, the root bridge
+is a designated switch in a bridged network that serves as a reference point
+for the spanning tree algorithm to create a loop-free topology.
+
+Here's how the STP works and root bridge is chosen:
+  1. Bridge Priority: Each bridge running a spanning tree protocol, has a
+     configurable Bridge Priority value. The lower the value, the higher the
+     priority. By default, the Bridge Priority is set to a standard value
+     (e.g., 32768).
+  2. Bridge ID: The Bridge ID is composed of two components: Bridge Priority
+     and the MAC address of the bridge. It uniquely identifies each bridge
+     in the network. The Bridge ID is used to compare the priorities of
+     different bridges.
+  3. Bridge Election: When the network starts, all bridges initially assume
+     that they are the root bridge. They start advertising Bridge Protocol
+     Data Units (BPDU) to their neighbors, containing their Bridge ID and
+     other information.
+  4. BPDU Comparison: Bridges exchange BPDUs to determine the root bridge.
+     Each bridge examines the received BPDUs, including the Bridge Priority
+     and Bridge ID, to determine if it should adjust its own priorities.
+     The bridge with the lowest Bridge ID will become the root bridge.
+  5. Root Bridge Announcement: Once the root bridge is determined, it sends
+     BPDUs with information about the root bridge to all other bridges in the
+     network. This information is used by other bridges to calculate the
+     shortest path to the root bridge and, in doing so, create a loop-free
+     topology.
+  6. Forwarding Ports: After the root bridge is selected and the spanning tree
+     topology is established, each bridge determines which of its ports should
+     be in the forwarding state (used for data traffic) and which should be in
+     the blocking state (used to prevent loops). The root bridge's ports are
+     all in the forwarding state. while other bridges have some ports in the
+     blocking state to avoid loops.
+  7. Root Ports: After the root bridge is selected and the spanning tree
+     topology is established, each non-root bridge processes incoming
+     BPDUs and determines which of its ports provides the shortest path to the
+     root bridge based on the information in the received BPDUs. This port is
+     designated as the root port. And it is in the Forwarding state, allowing
+     it to actively forward network traffic.
+  8. Designated ports: A designated port is the port through which the non-root
+     bridge will forward traffic towards the designated segment. Designated ports
+     are placed in the Forwarding state. All other ports on the non-root
+     bridge that are not designated for specific segments are placed in the
+     Blocking state to prevent network loops.
+
+STP ensures network convergence by calculating the shortest path and disabling
+redundant links. When network topology changes occur (e.g., a link failure),
+STP recalculates the network topology to restore connectivity while avoiding loops.
+
+Proper configuration of STP parameters, such as the bridge priority, can
+influence which bridge becomes the Root Bridge. Careful configuration can
+optimize network performance and path selection.
+
 FAQ
 ===
 
-- 
2.41.0

Re: [PATCH net-next 05/10] docs: bridge: add STP doc

[Vladimir Oltean]

On Fri, Nov 17, 2023 at 05:31:40PM +0800, Hangbin Liu wrote:
> +STP
> +===

I think it would be very good to say a few words about the user space
STP helper at /sbin/bridge-stp, and that the kernel only has full support
for the legacy STP, whereas newer protocols are all handled in user
space. But I don't know a lot of technical details about it, so I would
hope somebody else chimes in with a paragraph inserted here somewhere :)

Re: [PATCH net-next 05/10] docs: bridge: add STP doc

[Hangbin Liu]

On Mon, Nov 20, 2023 at 01:39:47PM +0200, Vladimir Oltean wrote:
> On Fri, Nov 17, 2023 at 05:31:40PM +0800, Hangbin Liu wrote:
> > +STP
> > +===
> 
> I think it would be very good to say a few words about the user space
> STP helper at /sbin/bridge-stp, and that the kernel only has full support
> for the legacy STP, whereas newer protocols are all handled in user
> space. But I don't know a lot of technical details about it, so I would
> hope somebody else chimes in with a paragraph inserted here somewhere :)

Hmm, I google searched but can't find this tool. Nikolay, is this tool still
widely used? Do you know where I can find the source code/doc of it?

Thanks
Hangbin

Re: [PATCH net-next 05/10] docs: bridge: add STP doc

[Nikolay Aleksandrov]

On 11/21/23 05:02, Hangbin Liu wrote:
> On Mon, Nov 20, 2023 at 01:39:47PM +0200, Vladimir Oltean wrote:
>> On Fri, Nov 17, 2023 at 05:31:40PM +0800, Hangbin Liu wrote:
>>> +STP
>>> +===
>>
>> I think it would be very good to say a few words about the user space
>> STP helper at /sbin/bridge-stp, and that the kernel only has full support
>> for the legacy STP, whereas newer protocols are all handled in user
>> space. But I don't know a lot of technical details about it, so I would
>> hope somebody else chimes in with a paragraph inserted here somewhere :)
> 
> Hmm, I google searched but can't find this tool. Nikolay, is this tool still
> widely used? Do you know where I can find the source code/doc of it?
> 
> Thanks
> Hangbin

Man.. you're documenting the bridge, please check its source code and
you'll have your answer. "bridge-stp" is not a single tool, rather than
a device for the bridge to start/stop user-space stp when requested.
As an example here's the first google result:
https://github.com/mstpd/mstpd/blob/master/bridge-stp.in

Re: [PATCH net-next 05/10] docs: bridge: add STP doc

[Hangbin Liu]

Hi Nikolay,

On Fri, Nov 24, 2023 at 03:18:19PM +0200, Nikolay Aleksandrov wrote:
> On 11/21/23 05:02, Hangbin Liu wrote:
> > On Mon, Nov 20, 2023 at 01:39:47PM +0200, Vladimir Oltean wrote:
> > > On Fri, Nov 17, 2023 at 05:31:40PM +0800, Hangbin Liu wrote:
> > > > +STP
> > > > +===
> > > 
> > > I think it would be very good to say a few words about the user space
> > > STP helper at /sbin/bridge-stp, and that the kernel only has full support
> > > for the legacy STP, whereas newer protocols are all handled in user
> > > space. But I don't know a lot of technical details about it, so I would
> > > hope somebody else chimes in with a paragraph inserted here somewhere :)
> > 
> > Hmm, I google searched but can't find this tool. Nikolay, is this tool still
> > widely used? Do you know where I can find the source code/doc of it?
> > 
> > Thanks
> > Hangbin
> 
> Man.. you're documenting the bridge, please check its source code and
> you'll have your answer. "bridge-stp" is not a single tool, rather than

Thanks for your reply. I'm not very familiar with the bridge STP part. The
#define BR_STP_PROG     "/sbin/bridge-stp"
mislead me to think that the bridge-stp is a userspace tool..

> a device for the bridge to start/stop user-space stp when requested.
> As an example here's the first google result:
> https://github.com/mstpd/mstpd/blob/master/bridge-stp.in

Last time I just searched bridge-stp and didn't find any useful result.
This time with "sbin/bridge-stp" I saw the doc you pointed. Thanks for your
reference.

So for the STP part, How about add a paragraph like:

The user space STP helper *bridge-stp* is a program to control whether to use
user mode spanning tree. The `/sbin/bridge-stp <bridge> <start|stop>` is
called by the kernel when STP is enabled/disabled on a bridge
(via `brctl stp <bridge> <on|off>` or `ip link set <bridge> type bridge
stp_state <0|1>`).  The kernel enables user_stp mode if that command returns
0, or enables kernel_stp mode if that command returns any other value.


Thanks
Hangbin

Re: [PATCH net-next 05/10] docs: bridge: add STP doc

[Stephen Hemminger]

On Tue, 21 Nov 2023 11:02:55 +0800
Hangbin Liu <liuhangbin@gmail.com> wrote:

> On Mon, Nov 20, 2023 at 01:39:47PM +0200, Vladimir Oltean wrote:
> > On Fri, Nov 17, 2023 at 05:31:40PM +0800, Hangbin Liu wrote:  
> > > +STP
> > > +===  
> > 
> > I think it would be very good to say a few words about the user space
> > STP helper at /sbin/bridge-stp, and that the kernel only has full support
> > for the legacy STP, whereas newer protocols are all handled in user
> > space. But I don't know a lot of technical details about it, so I would
> > hope somebody else chimes in with a paragraph inserted here somewhere :)  
> 
> Hmm, I google searched but can't find this tool. Nikolay, is this tool still
> widely used? Do you know where I can find the source code/doc of it?
> 
> Thanks
> Hangbin

Older one is here (no longer maintained):
  https://github.com/shemminger/RSTP
Other version is here:
  https://github.com/mstpd/mstpd

[PATCH net-next 06/10] docs: bridge: add VLAN doc

[Hangbin Liu]

Add VLAN part for bridge document.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 Documentation/networking/bridge.rst | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst
index 1fd339e48129..f70f42ab7396 100644
--- a/Documentation/networking/bridge.rst
+++ b/Documentation/networking/bridge.rst
@@ -136,6 +136,35 @@ Proper configuration of STP parameters, such as the bridge priority, can
 influence which bridge becomes the Root Bridge. Careful configuration can
 optimize network performance and path selection.
 
+VLAN
+====
+
+A LAN (Local Area Network) is a network that covers a small geographic area,
+typically within a single building or a campus. LANs are used to connect
+computers, servers, printers, and other networked devices within a localized
+area. LANs can be wired (using Ethernet cables) or wireless (using Wi-Fi).
+
+A VLAN (Virtual Local Area Network) is a logical segmentation of a physical
+network into multiple isolated broadcast domains. VLANs are used to divide
+a single physical LAN into multiple virtual LANs, allowing different groups of
+devices to communicate as if they were on separate physical networks.
+
+Typically there are two VLAN implementations, IEEE 802.1Q and IEEE 802.1ad
+(also known as QinQ). IEEE 802.1Q is a standard for VLAN tagging in Ethernet
+networks. It allows network administrators to create logical VLANs on a
+physical network and tag Ethernet frames with VLAN information, which is
+called *VLAN-tagged frames*. IEEE 802.1ad, commonly known as QinQ or Double
+VLAN, is an extension of the IEEE 802.1Q standard. QinQ allows for the
+stacking of multiple VLAN tags within a single Ethernet frame. The Linux
+bridge supports both the IEEE 802.1Q and `802.1AD
+<https://lore.kernel.org/netdev/1402401565-15423-1-git-send-email-makita.toshiaki@lab.ntt.co.jp/>`_
+protocol for VLAN tagging.
+
+`VLAN filtering <https://lore.kernel.org/netdev/1360792820-14116-1-git-send-email-vyasevic@redhat.com/>`_
+on a bridge is disabled by default. After enabling VLAN filtering on a bridge,
+it will start forwarding frames to appropriate destinations based on their
+destination MAC address and VLAN tag (both must match).
+
 FAQ
 ===
 
-- 
2.41.0

[PATCH net-next 07/10] docs: bridge: add multicast doc

[Hangbin Liu]

Add multicast part for bridge document.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 Documentation/networking/bridge.rst | 55 +++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst
index f70f42ab7396..62cb6695cd22 100644
--- a/Documentation/networking/bridge.rst
+++ b/Documentation/networking/bridge.rst
@@ -165,6 +165,61 @@ on a bridge is disabled by default. After enabling VLAN filtering on a bridge,
 it will start forwarding frames to appropriate destinations based on their
 destination MAC address and VLAN tag (both must match).
 
+Multicast
+=========
+
+The Linux bridge driver has multicast support allowing it to process Internet
+Group Management Protocol (IGMP) or Multicast Listener Discovery (MLD)
+messages, and to efficiently forward multicast data packets. The bridge
+driver support IGMPv2/IGMPv3 and MLDv1/MLDv2.
+
+Multicast snooping
+------------------
+
+Multicast snooping is a networking technology that allows network switches
+to intelligently manage multicast traffic within a local area network (LAN).
+
+The switch maintains a multicast group table, which records the association
+between multicast group addresses and the ports where hosts have joined these
+groups. The group table is dynamically updated based on the IGMP/MLD messages
+received. With the multicast group information gathered through snooping, the
+switch optimizes the forwarding of multicast traffic. Instead of blindly
+broadcasting the multicast traffic to all ports, it sends the multicast
+traffic based on the destination MAC address only to ports which have joined
+the respective destination multicast group.
+
+When created, the Linux bridge devices have multicast snooping enabled by
+default. It maintains a Multicast forwarding database (MDB) which keeps track
+of port and group relationships.
+
+IGMPv3/MLDv2 EHT support
+------------------------
+
+The Linux bridge supports IGMPv3/MLDv2 EHT (Explicit Host Tracking), which
+was added by `474ddb37fa3a ("net: bridge: multicast: add EHT allow/block handling")
+<https://lore.kernel.org/netdev/20210120145203.1109140-1-razor@blackwall.org/>`_
+
+The explicit host tracking enables the device to keep track of each
+individual host that is joined to a particular group or channel. The main
+benefit of the explicit host tracking in IGMP is to allow minimal leave
+latencies when a host leaves a multicast group or channel.
+
+The length of time between a host wanting to leave and a device stopping
+traffic forwarding is called the IGMP leave latency. A device configured
+with IGMPv3 or MLDv2 and explicit tracking can immediately stop forwarding
+traffic if the last host to request to receive traffic from the device
+indicates that it no longer wants to receive traffic. The leave latency
+is thus bound only by the packet transmission latencies in the multiaccess
+network and the processing time in the device.
+
+Other multicast features
+------------------------
+The Linux bridge also supports `per-VLAN multicast snooping
+<https://lore.kernel.org/netdev/20210719170637.435541-1-razor@blackwall.org/>`_,
+which is disabled by default but can be enabled. And `Multicast Router Discovery
+<https://lore.kernel.org/netdev/20190121062628.2710-1-linus.luessing@c0d3.blue/>`_,
+which help identify the location of multicast routers.
+
 FAQ
 ===
 
-- 
2.41.0

[PATCH net-next 08/10] docs: bridge: add switchdev doc

[Hangbin Liu]

Add switchdev part for bridge document.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 Documentation/networking/bridge.rst | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst
index 62cb6695cd22..f42c19e59268 100644
--- a/Documentation/networking/bridge.rst
+++ b/Documentation/networking/bridge.rst
@@ -220,6 +220,24 @@ which is disabled by default but can be enabled. And `Multicast Router Discovery
 <https://lore.kernel.org/netdev/20190121062628.2710-1-linus.luessing@c0d3.blue/>`_,
 which help identify the location of multicast routers.
 
+Switchdev
+=========
+
+Linux Bridge Switchdev is a feature in the Linux kernel that extends the
+capabilities of the traditional Linux bridge to work more efficiently with
+hardware switches that support switchdev. With Linux Bridge Switchdev, certain
+networking functions like forwarding, filtering, and learning of Ethernet
+frames can be offloaded to a hardware switch. This offloading reduces the
+burden on the Linux kernel and CPU, leading to improved network performance
+and lower latency.
+
+To use Linux Bridge Switchdev, you need hardware switches that support the
+switchdev interface. This means that the switch hardware needs to have the
+necessary drivers and functionality to work in conjunction with the Linux
+kernel.
+
+Please see the :ref:`switchdev` document for more details.
+
 FAQ
 ===
 
-- 
2.41.0

Re: [PATCH net-next 08/10] docs: bridge: add switchdev doc

[Vladimir Oltean]

On Fri, Nov 17, 2023 at 05:31:43PM +0800, Hangbin Liu wrote:
> Add switchdev part for bridge document.
> 
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
> ---

Reviewed-by: Vladimir Oltean <olteanv@gmail.com>

[PATCH net-next 09/10] docs: bridge: add netfilter doc

[Hangbin Liu]

Add netfilter part for bridge document.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 Documentation/networking/bridge.rst | 36 +++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst
index f42c19e59268..772bbe28aefe 100644
--- a/Documentation/networking/bridge.rst
+++ b/Documentation/networking/bridge.rst
@@ -238,6 +238,42 @@ kernel.
 
 Please see the :ref:`switchdev` document for more details.
 
+Netfilter
+=========
+
+The bridge netfilter module is a legacy feature that allows to filter bridged
+packets with iptables and ip6tables. Its use is discouraged. Users should
+consider using nftables for packet filtering.
+
+The older ebtables tool is more feature-limited compared to nftables, but
+just like nftables it doesn't need this module either to function.
+
+The br_netfilter module intercepts packets entering the bridge, performs
+minimal sanity tests on ipv4 and ipv6 packets and then pretends that
+these packets are being routed, not bridged. br_netfilter then calls
+the ip and ipv6 netfilter hooks from the bridge layer, i.e. ip(6)tables
+rulesets will also see these packets.
+
+br_netfilter is also the reason for the iptables *physdev* match:
+This match is the only way to reliably tell routed and bridged packets
+apart in an iptables ruleset.
+
+Note that ebtables and nftables will work fine without the br_netfilter module.
+iptables/ip6tables/arptables do not work for bridged traffic because they
+plug in the routing stack. nftables rules in ip/ip6/inet/arp families won't
+see traffic that is forwarded by a bridge either, but that's very much how it
+should be.
+
+Historically the feature set of ebtables was very limited (it still is),
+this module was added to pretend packets are routed and invoke the ipv4/ipv6
+netfilter hooks from the bridge so users had access to the more feature-rich
+iptables matching capabilities (including conntrack). nftables doesn't have
+this limitation, pretty much all features work regardless of the protocol family.
+
+So, br_netfilter is only needed if users, for some reason, need to use
+ip(6)tables to filter packets forwarded by the bridge, or NAT bridged
+traffic. For pure link layer filtering, this module isn't needed.
+
 FAQ
 ===
 
-- 
2.41.0

[PATCH net-next 10/10] docs: bridge: add other features

[Hangbin Liu]

Add some features that are not appropriate for the existing section to
the "Others" part of the bridge document.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 Documentation/networking/bridge.rst | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Documentation/networking/bridge.rst b/Documentation/networking/bridge.rst
index 772bbe28aefe..54118d9da2a4 100644
--- a/Documentation/networking/bridge.rst
+++ b/Documentation/networking/bridge.rst
@@ -274,6 +274,20 @@ So, br_netfilter is only needed if users, for some reason, need to use
 ip(6)tables to filter packets forwarded by the bridge, or NAT bridged
 traffic. For pure link layer filtering, this module isn't needed.
 
+Other Features
+==============
+
+The Linux bridge also supports `IEEE 802.11 Proxy ARP
+<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=958501163ddd6ea22a98f94fa0e7ce6d4734e5c4>`_,
+`Media Redundancy Protocol (MRP)
+<https://lore.kernel.org/netdev/20200426132208.3232-1-horatiu.vultur@microchip.com/>`_,
+`Media Redundancy Protocol (MRP) LC mode
+<https://lore.kernel.org/r/20201124082525.273820-1-horatiu.vultur@microchip.com>`_,
+`IEEE 802.1X port authentication
+<https://lore.kernel.org/netdev/20220218155148.2329797-1-schultz.hans+netdev@gmail.com/>`_,
+and `MAC Authentication Bypass (MAB)
+<https://lore.kernel.org/netdev/20221101193922.2125323-2-idosch@nvidia.com/>`_.
+
 FAQ
 ===
 
-- 
2.41.0