Re: [Bridge] [PATCH net-next mlxsw v2 07/16] net: bridge: Maintain number of MDB entries in net_bridge_mcast_port
Nikolay Aleksandrov writes: > On 01/02/2023 19:28, Petr Machata wrote: >> @@ -668,6 +692,82 @@ void br_multicast_del_group_src(struct >> net_bridge_group_src *src, >> __br_multicast_del_group_src(src); >> } >> >> +static int >> +br_multicast_port_ngroups_inc_one(struct net_bridge_mcast_port *pmctx, >> + struct netlink_ext_ack *extack) >> +{ >> +if (pmctx->mdb_max_entries && >> +pmctx->mdb_n_entries >= pmctx->mdb_max_entries) > > These should be using *_ONCE() because of the next patch. > KCSAN might be sad otherwise. :) I didn't see any (relevant) KCSAN warnings on x86_64. But yeah, it (and the others you cited) should be *_ONCE.
Re: [Bridge] [PATCH net-next mlxsw v2 07/16] net: bridge: Maintain number of MDB entries in net_bridge_mcast_port
On 02/02/2023 10:56, Nikolay Aleksandrov wrote: > On 01/02/2023 19:28, Petr Machata wrote: >> The MDB maintained by the bridge is limited. When the bridge is configured >> for IGMP / MLD snooping, a buggy or malicious client can easily exhaust its >> capacity. In SW datapath, the capacity is configurable through the >> IFLA_BR_MCAST_HASH_MAX parameter, but ultimately is finite. Obviously a >> similar limit exists in the HW datapath for purposes of offloading. >> >> In order to prevent the issue of unilateral exhaustion of MDB resources, >> introduce two parameters in each of two contexts: >> >> - Per-port and per-port-VLAN number of MDB entries that the port >> is member in. >> >> - Per-port and (when BROPT_MCAST_VLAN_SNOOPING_ENABLED is enabled) >> per-port-VLAN maximum permitted number of MDB entries, or 0 for >> no limit. >> >> The per-port multicast context is used for tracking of MDB entries for the >> port as a whole. This is available for all bridges. >> >> The per-port-VLAN multicast context is then only available on >> VLAN-filtering bridges on VLANs that have multicast snooping on. >> >> With these changes in place, it will be possible to configure MDB limit for >> bridge as a whole, or any one port as a whole, or any single port-VLAN. >> >> Note that unlike the global limit, exhaustion of the per-port and >> per-port-VLAN maximums does not cause disablement of multicast snooping. >> It is also permitted to configure the local limit larger than hash_max, >> even though that is not useful. >> >> In this patch, introduce only the accounting for number of entries, and the >> max field itself, but not the means to toggle the max. The next patch >> introduces the netlink APIs to toggle and read the values. >> >> Signed-off-by: Petr Machata >> --- >> >> Notes: >> v2: >> - In br_multicast_port_ngroups_inc_one(), bounce >> if n>=max, not if n==max >> - Adjust extack messages to mention ngroups, now that >> the bounces appear when n>=max, not n==max >> - In __br_multicast_enable_port_ctx(), do not reset >> max to 0. Also do not count number of entries by >> going through _inc, as that would end up incorrectly >> bouncing the entries. >> >> net/bridge/br_multicast.c | 132 +- >> net/bridge/br_private.h | 2 + >> 2 files changed, 133 insertions(+), 1 deletion(-) >> >> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c >> index 51b622afdb67..e7ae339a8757 100644 >> --- a/net/bridge/br_multicast.c >> +++ b/net/bridge/br_multicast.c >> @@ -31,6 +31,7 @@ >> #include >> #include >> #endif >> +#include >> >> #include "br_private.h" >> #include "br_private_mcast_eht.h" >> @@ -234,6 +235,29 @@ br_multicast_pg_to_port_ctx(const struct >> net_bridge_port_group *pg) >> return pmctx; >> } >> >> +static struct net_bridge_mcast_port * >> +br_multicast_port_vid_to_port_ctx(struct net_bridge_port *port, u16 vid) >> +{ >> +struct net_bridge_mcast_port *pmctx = NULL; >> +struct net_bridge_vlan *vlan; >> + >> +lockdep_assert_held_once(>br->multicast_lock); >> + >> +if (!br_opt_get(port->br, BROPT_MCAST_VLAN_SNOOPING_ENABLED)) >> +return NULL; >> + >> +/* Take RCU to access the vlan. */ >> +rcu_read_lock(); >> + >> +vlan = br_vlan_find(nbp_vlan_group_rcu(port), vid); >> +if (vlan && !br_multicast_port_ctx_vlan_disabled(>port_mcast_ctx)) >> +pmctx = >port_mcast_ctx; >> + >> +rcu_read_unlock(); >> + >> +return pmctx; >> +} >> + >> /* when snooping we need to check if the contexts should be used >> * in the following order: >> * - if pmctx is non-NULL (port), check if it should be used >> @@ -668,6 +692,82 @@ void br_multicast_del_group_src(struct >> net_bridge_group_src *src, >> __br_multicast_del_group_src(src); >> } >> >> +static int >> +br_multicast_port_ngroups_inc_one(struct net_bridge_mcast_port *pmctx, >> + struct netlink_ext_ack *extack) >> +{ >> +if (pmctx->mdb_max_entries && >> +pmctx->mdb_n_entries >= pmctx->mdb_max_entries) > > These should be using *_ONCE() because of the next patch. > KCSAN might be sad otherwise. :) > >> +return -E2BIG; >> + >> +pmctx->mdb_n_entries++; > > WRITE_ONCE() > >> +return 0; >> +} >> + >> +static void br_multicast_port_ngroups_dec_one(struct net_bridge_mcast_port >> *pmctx) >> +{ >> +WARN_ON_ONCE(pmctx->mdb_n_entries-- == 0); > > READ_ONCE() err, I meant WRITE_ONCE() of course. :) Need to get coffee. > >> +} >> +
Re: [Bridge] [PATCH net-next mlxsw v2 07/16] net: bridge: Maintain number of MDB entries in net_bridge_mcast_port
On 01/02/2023 19:28, Petr Machata wrote: > The MDB maintained by the bridge is limited. When the bridge is configured > for IGMP / MLD snooping, a buggy or malicious client can easily exhaust its > capacity. In SW datapath, the capacity is configurable through the > IFLA_BR_MCAST_HASH_MAX parameter, but ultimately is finite. Obviously a > similar limit exists in the HW datapath for purposes of offloading. > > In order to prevent the issue of unilateral exhaustion of MDB resources, > introduce two parameters in each of two contexts: > > - Per-port and per-port-VLAN number of MDB entries that the port > is member in. > > - Per-port and (when BROPT_MCAST_VLAN_SNOOPING_ENABLED is enabled) > per-port-VLAN maximum permitted number of MDB entries, or 0 for > no limit. > > The per-port multicast context is used for tracking of MDB entries for the > port as a whole. This is available for all bridges. > > The per-port-VLAN multicast context is then only available on > VLAN-filtering bridges on VLANs that have multicast snooping on. > > With these changes in place, it will be possible to configure MDB limit for > bridge as a whole, or any one port as a whole, or any single port-VLAN. > > Note that unlike the global limit, exhaustion of the per-port and > per-port-VLAN maximums does not cause disablement of multicast snooping. > It is also permitted to configure the local limit larger than hash_max, > even though that is not useful. > > In this patch, introduce only the accounting for number of entries, and the > max field itself, but not the means to toggle the max. The next patch > introduces the netlink APIs to toggle and read the values. > > Signed-off-by: Petr Machata > --- > > Notes: > v2: > - In br_multicast_port_ngroups_inc_one(), bounce > if n>=max, not if n==max > - Adjust extack messages to mention ngroups, now that > the bounces appear when n>=max, not n==max > - In __br_multicast_enable_port_ctx(), do not reset > max to 0. Also do not count number of entries by > going through _inc, as that would end up incorrectly > bouncing the entries. > > net/bridge/br_multicast.c | 132 +- > net/bridge/br_private.h | 2 + > 2 files changed, 133 insertions(+), 1 deletion(-) > > diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c > index 51b622afdb67..e7ae339a8757 100644 > --- a/net/bridge/br_multicast.c > +++ b/net/bridge/br_multicast.c > @@ -31,6 +31,7 @@ > #include > #include > #endif > +#include > > #include "br_private.h" > #include "br_private_mcast_eht.h" > @@ -234,6 +235,29 @@ br_multicast_pg_to_port_ctx(const struct > net_bridge_port_group *pg) > return pmctx; > } > > +static struct net_bridge_mcast_port * > +br_multicast_port_vid_to_port_ctx(struct net_bridge_port *port, u16 vid) > +{ > + struct net_bridge_mcast_port *pmctx = NULL; > + struct net_bridge_vlan *vlan; > + > + lockdep_assert_held_once(>br->multicast_lock); > + > + if (!br_opt_get(port->br, BROPT_MCAST_VLAN_SNOOPING_ENABLED)) > + return NULL; > + > + /* Take RCU to access the vlan. */ > + rcu_read_lock(); > + > + vlan = br_vlan_find(nbp_vlan_group_rcu(port), vid); > + if (vlan && !br_multicast_port_ctx_vlan_disabled(>port_mcast_ctx)) > + pmctx = >port_mcast_ctx; > + > + rcu_read_unlock(); > + > + return pmctx; > +} > + > /* when snooping we need to check if the contexts should be used > * in the following order: > * - if pmctx is non-NULL (port), check if it should be used > @@ -668,6 +692,82 @@ void br_multicast_del_group_src(struct > net_bridge_group_src *src, > __br_multicast_del_group_src(src); > } > > +static int > +br_multicast_port_ngroups_inc_one(struct net_bridge_mcast_port *pmctx, > + struct netlink_ext_ack *extack) > +{ > + if (pmctx->mdb_max_entries && > + pmctx->mdb_n_entries >= pmctx->mdb_max_entries) These should be using *_ONCE() because of the next patch. KCSAN might be sad otherwise. :) > + return -E2BIG; > + > + pmctx->mdb_n_entries++; WRITE_ONCE() > + return 0; > +} > + > +static void br_multicast_port_ngroups_dec_one(struct net_bridge_mcast_port > *pmctx) > +{ > + WARN_ON_ONCE(pmctx->mdb_n_entries-- == 0); READ_ONCE() > +} > + > +static int br_multicast_port_ngroups_inc(struct net_bridge_port *port, > + const struct br_ip *group, > + struct netlink_ext_ack *extack) > +{ > + struct net_bridge_mcast_port *pmctx; > + int err; > + > + lockdep_assert_held_once(>br->multicast_lock); > + > + /* Always count on the port context. */ > + err = br_multicast_port_ngroups_inc_one(>multicast_ctx, extack); > + if (err) { > + NL_SET_ERR_MSG_FMT_MOD(extack, "Port is already in %u groups, > and mcast_max_groups=%u", > +