From dc452a471dbae8aca8257c565174212620880093 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Fri, 10 Dec 2021 01:34:37 +0200 Subject: net: dsa: introduce tagger-owned storage for private and shared data Ansuel is working on register access over Ethernet for the qca8k switch family. This requires the qca8k tagging protocol driver to receive frames which aren't intended for the network stack, but instead for the qca8k switch driver itself. The dp->priv is currently the prevailing method for passing data back and forth between the tagging protocol driver and the switch driver. However, this method is riddled with caveats. The DSA design allows in principle for any switch driver to return any protocol it desires in ->get_tag_protocol(). The dsa_loop driver can be modified to do just that. But in the current design, the memory behind dp->priv has to be allocated by the switch driver, so if the tagging protocol is paired to an unexpected switch driver, we may end up in NULL pointer dereferences inside the kernel, or worse (a switch driver may allocate dp->priv according to the expectations of a different tagger). The latter possibility is even more plausible considering that DSA switches can dynamically change tagging protocols in certain cases (dsa <-> edsa, ocelot <-> ocelot-8021q), and the current design lends itself to mistakes that are all too easy to make. This patch proposes that the tagging protocol driver should manage its own memory, instead of relying on the switch driver to do so. After analyzing the different in-tree needs, it can be observed that the required tagger storage is per switch, therefore a ds->tagger_data pointer is introduced. In principle, per-port storage could also be introduced, although there is no need for it at the moment. Future changes will replace the current usage of dp->priv with ds->tagger_data. We define a "binding" event between the DSA switch tree and the tagging protocol. During this binding event, the tagging protocol's ->connect() method is called first, and this may allocate some memory for each switch of the tree. Then a cross-chip notifier is emitted for the switches within that tree, and they are given the opportunity to fix up the tagger's memory (for example, they might set up some function pointers that represent virtual methods for consuming packets). Because the memory is owned by the tagger, there exists a ->disconnect() method for the tagger (which is the place to free the resources), but there doesn't exist a ->disconnect() method for the switch driver. This is part of the design. The switch driver should make minimal use of the public part of the tagger data, and only after type-checking it using the supplied "proto" argument. In the code there are in fact two binding events, one is the initial event in dsa_switch_setup_tag_protocol(). At this stage, the cross chip notifier chains aren't initialized, so we call each switch's connect() method by hand. Then there is dsa_tree_bind_tag_proto() during dsa_tree_change_tag_proto(), and here we have an old protocol and a new one. We first connect to the new one before disconnecting from the old one, to simplify error handling a bit and to ensure we remain in a valid state at all times. Co-developed-by: Ansuel Smith Signed-off-by: Ansuel Smith Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller --- include/net/dsa.h | 12 +++++++++ net/dsa/dsa2.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++--- net/dsa/dsa_priv.h | 1 + net/dsa/switch.c | 14 +++++++++++ 4 files changed, 96 insertions(+), 4 deletions(-) --- a/include/net/dsa.h +++ b/include/net/dsa.h @@ -80,12 +80,15 @@ enum dsa_tag_protocol { }; struct dsa_switch; +struct dsa_switch_tree; struct dsa_device_ops { struct sk_buff *(*xmit)(struct sk_buff *skb, struct net_device *dev); struct sk_buff *(*rcv)(struct sk_buff *skb, struct net_device *dev); void (*flow_dissect)(const struct sk_buff *skb, __be16 *proto, int *offset); + int (*connect)(struct dsa_switch_tree *dst); + void (*disconnect)(struct dsa_switch_tree *dst); unsigned int needed_headroom; unsigned int needed_tailroom; const char *name; @@ -329,6 +332,8 @@ struct dsa_switch { */ void *priv; + void *tagger_data; + /* * Configuration data for this switch. */ @@ -584,6 +589,13 @@ struct dsa_switch_ops { enum dsa_tag_protocol mprot); int (*change_tag_protocol)(struct dsa_switch *ds, int port, enum dsa_tag_protocol proto); + /* + * Method for switch drivers to connect to the tagging protocol driver + * in current use. The switch driver can provide handlers for certain + * types of packets for switch management. + */ + int (*connect_tag_protocol)(struct dsa_switch *ds, + enum dsa_tag_protocol proto); /* Optional switch-wide initialization and destruction methods */ int (*setup)(struct dsa_switch *ds); --- a/net/dsa/dsa2.c +++ b/net/dsa/dsa2.c @@ -230,8 +230,12 @@ static struct dsa_switch_tree *dsa_tree_ static void dsa_tree_free(struct dsa_switch_tree *dst) { - if (dst->tag_ops) + if (dst->tag_ops) { + if (dst->tag_ops->disconnect) + dst->tag_ops->disconnect(dst); + dsa_tag_driver_put(dst->tag_ops); + } list_del(&dst->list); kfree(dst); } @@ -805,7 +809,7 @@ static int dsa_switch_setup_tag_protocol int port, err; if (tag_ops->proto == dst->default_proto) - return 0; + goto connect; for (port = 0; port < ds->num_ports; port++) { if (!dsa_is_cpu_port(ds, port)) @@ -821,6 +825,17 @@ static int dsa_switch_setup_tag_protocol } } +connect: + if (ds->ops->connect_tag_protocol) { + err = ds->ops->connect_tag_protocol(ds, tag_ops->proto); + if (err) { + dev_err(ds->dev, + "Unable to connect to tag protocol \"%s\": %pe\n", + tag_ops->name, ERR_PTR(err)); + return err; + } + } + return 0; } @@ -1132,6 +1147,46 @@ static void dsa_tree_teardown(struct dsa dst->setup = false; } +static int dsa_tree_bind_tag_proto(struct dsa_switch_tree *dst, + const struct dsa_device_ops *tag_ops) +{ + const struct dsa_device_ops *old_tag_ops = dst->tag_ops; + struct dsa_notifier_tag_proto_info info; + int err; + + dst->tag_ops = tag_ops; + + /* Notify the new tagger about the connection to this tree */ + if (tag_ops->connect) { + err = tag_ops->connect(dst); + if (err) + goto out_revert; + } + + /* Notify the switches from this tree about the connection + * to the new tagger + */ + info.tag_ops = tag_ops; + err = dsa_tree_notify(dst, DSA_NOTIFIER_TAG_PROTO_CONNECT, &info); + if (err && err != -EOPNOTSUPP) + goto out_disconnect; + + /* Notify the old tagger about the disconnection from this tree */ + if (old_tag_ops->disconnect) + old_tag_ops->disconnect(dst); + + return 0; + +out_disconnect: + /* Revert the new tagger's connection to this tree */ + if (tag_ops->disconnect) + tag_ops->disconnect(dst); +out_revert: + dst->tag_ops = old_tag_ops; + + return err; +} + /* Since the dsa/tagging sysfs device attribute is per master, the assumption * is that all DSA switches within a tree share the same tagger, otherwise * they would have formed disjoint trees (different "dsa,member" values). @@ -1164,12 +1219,15 @@ int dsa_tree_change_tag_proto(struct dsa goto out_unlock; } + /* Notify the tag protocol change */ info.tag_ops = tag_ops; err = dsa_tree_notify(dst, DSA_NOTIFIER_TAG_PROTO, &info); if (err) - goto out_unwind_tagger; + return err; - dst->tag_ops = tag_ops; + err = dsa_tree_bind_tag_proto(dst, tag_ops); + if (err) + goto out_unwind_tagger; rtnl_unlock(); @@ -1257,6 +1315,7 @@ static int dsa_port_parse_cpu(struct dsa struct dsa_switch_tree *dst = ds->dst; const struct dsa_device_ops *tag_ops; enum dsa_tag_protocol default_proto; + int err; /* Find out which protocol the switch would prefer. */ default_proto = dsa_get_tag_protocol(dp, master); @@ -1304,6 +1363,12 @@ static int dsa_port_parse_cpu(struct dsa */ dsa_tag_driver_put(tag_ops); } else { + if (tag_ops->connect) { + err = tag_ops->connect(dst); + if (err) + return err; + } + dst->tag_ops = tag_ops; } --- a/net/dsa/dsa_priv.h +++ b/net/dsa/dsa_priv.h @@ -37,6 +37,7 @@ enum { DSA_NOTIFIER_VLAN_DEL, DSA_NOTIFIER_MTU, DSA_NOTIFIER_TAG_PROTO, + DSA_NOTIFIER_TAG_PROTO_CONNECT, DSA_NOTIFIER_MRP_ADD, DSA_NOTIFIER_MRP_DEL, DSA_NOTIFIER_MRP_ADD_RING_ROLE, --- a/net/dsa/switch.c +++ b/net/dsa/switch.c @@ -616,6 +616,17 @@ static int dsa_switch_change_tag_proto(s return 0; } +static int dsa_switch_connect_tag_proto(struct dsa_switch *ds, + struct dsa_notifier_tag_proto_info *info) +{ + const struct dsa_device_ops *tag_ops = info->tag_ops; + + if (!ds->ops->connect_tag_protocol) + return -EOPNOTSUPP; + + return ds->ops->connect_tag_protocol(ds, tag_ops->proto); +} + static int dsa_switch_mrp_add(struct dsa_switch *ds, struct dsa_notifier_mrp_info *info) { @@ -735,6 +746,9 @@ static int dsa_switch_event(struct notif case DSA_NOTIFIER_TAG_PROTO: err = dsa_switch_change_tag_proto(ds, info); break; + case DSA_NOTIFIER_TAG_PROTO_CONNECT: + err = dsa_switch_connect_tag_proto(ds, info); + break; case DSA_NOTIFIER_MRP_ADD: err = dsa_switch_mrp_add(ds, info); break;