From: Johannes Berg <johannes.berg@xxxxxxxxx> Extend drop reasons to make them usable by subsystems other than core by reserving the high 16 bits for a new subsystem ID, of which 0 of course is used for the existing reasons immediately. To still be able to have string reasons, restructure that code a bit to make the loopup under RCU, the only user of this (right now) is drop_monitor. Link: https://lore.kernel.org/netdev/00659771ed54353f92027702c5bbb84702da62ce.camel@xxxxxxxxxxxxxxxx Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> --- include/net/dropreason.h | 34 +++++++++++++++++++++---- net/core/drop_monitor.c | 32 +++++++++++++++++------- net/core/skbuff.c | 54 +++++++++++++++++++++++++++++++++++++--- 3 files changed, 103 insertions(+), 17 deletions(-) diff --git a/include/net/dropreason.h b/include/net/dropreason.h index c0a3ea806cd5..0f9508c6a34f 100644 --- a/include/net/dropreason.h +++ b/include/net/dropreason.h @@ -338,11 +338,24 @@ enum skb_drop_reason { * for another host. */ SKB_DROP_REASON_IPV6_NDISC_NS_OTHERHOST, - /** - * @SKB_DROP_REASON_MAX: the maximum of drop reason, which shouldn't be - * used as a real 'reason' + + /** @SKB_DROP_REASON_SUBSYS_MASK: subsystem mask in drop reasons, + * see &enum skb_drop_reason_subsys */ - SKB_DROP_REASON_MAX, + SKB_DROP_REASON_SUBSYS_MASK = 0xffff0000, +}; + +#define SKB_DROP_REASON_SUBSYS_SHIFT 16 + +/** + * enum skb_drop_reason_subsys - subsystem tag for (extended) drop reasons + */ +enum skb_drop_reason_subsys { + /** @SKB_DROP_REASON_SUBSYS_CORE: core drop reasons defined above */ + SKB_DROP_REASON_SUBSYS_CORE, + + /** @SKB_DROP_REASON_SUBSYS_NUM: number of subsystems defined */ + SKB_DROP_REASON_SUBSYS_NUM }; #define SKB_DR_INIT(name, reason) \ @@ -358,6 +371,17 @@ enum skb_drop_reason { SKB_DR_SET(name, reason); \ } while (0) -extern const char * const drop_reasons[]; +struct drop_reason_list { + const char * const *reasons; + size_t n_reasons; +}; + +/* Note: due to dynamic registrations, access must be under RCU */ +extern const struct drop_reason_list __rcu * +drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_NUM]; + +void drop_reasons_register_subsys(enum skb_drop_reason_subsys subsys, + const struct drop_reason_list *list); +void drop_reasons_unregister_subsys(enum skb_drop_reason_subsys subsys); #endif diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c index 5a782d1d8fd3..c6c60dc75b2d 100644 --- a/net/core/drop_monitor.c +++ b/net/core/drop_monitor.c @@ -21,6 +21,7 @@ #include <linux/workqueue.h> #include <linux/netlink.h> #include <linux/net_dropmon.h> +#include <linux/bitfield.h> #include <linux/percpu.h> #include <linux/timer.h> #include <linux/bitops.h> @@ -504,8 +505,6 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore, if (!nskb) return; - if (unlikely(reason >= SKB_DROP_REASON_MAX || reason <= 0)) - reason = SKB_DROP_REASON_NOT_SPECIFIED; cb = NET_DM_SKB_CB(nskb); cb->reason = reason; cb->pc = location; @@ -552,9 +551,9 @@ static size_t net_dm_in_port_size(void) } #define NET_DM_MAX_SYMBOL_LEN 40 +#define NET_DM_MAX_REASON_LEN 50 -static size_t net_dm_packet_report_size(size_t payload_len, - enum skb_drop_reason reason) +static size_t net_dm_packet_report_size(size_t payload_len) { size_t size; @@ -576,7 +575,7 @@ static size_t net_dm_packet_report_size(size_t payload_len, /* NET_DM_ATTR_PROTO */ nla_total_size(sizeof(u16)) + /* NET_DM_ATTR_REASON */ - nla_total_size(strlen(drop_reasons[reason]) + 1) + + nla_total_size(NET_DM_MAX_REASON_LEN + 1) + /* NET_DM_ATTR_PAYLOAD */ nla_total_size(payload_len); } @@ -610,6 +609,8 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb, size_t payload_len) { struct net_dm_skb_cb *cb = NET_DM_SKB_CB(skb); + const struct drop_reason_list *list = NULL; + unsigned int subsys, subsys_reason; char buf[NET_DM_MAX_SYMBOL_LEN]; struct nlattr *attr; void *hdr; @@ -627,9 +628,24 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb, NET_DM_ATTR_PAD)) goto nla_put_failure; + rcu_read_lock(); + subsys = u32_get_bits(cb->reason, SKB_DROP_REASON_SUBSYS_MASK); + if (subsys < SKB_DROP_REASON_SUBSYS_NUM) + list = rcu_dereference(drop_reasons_by_subsys[subsys]); + subsys_reason = cb->reason & ~SKB_DROP_REASON_SUBSYS_MASK; + if (!list || + subsys_reason >= list->n_reasons || + !list->reasons[subsys_reason] || + strlen(list->reasons[subsys_reason]) > NET_DM_MAX_REASON_LEN) { + list = rcu_dereference(drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_CORE]); + subsys_reason = SKB_DROP_REASON_NOT_SPECIFIED; + } if (nla_put_string(msg, NET_DM_ATTR_REASON, - drop_reasons[cb->reason])) + list->reasons[subsys_reason])) { + rcu_read_unlock(); goto nla_put_failure; + } + rcu_read_unlock(); snprintf(buf, sizeof(buf), "%pS", cb->pc); if (nla_put_string(msg, NET_DM_ATTR_SYMBOL, buf)) @@ -687,9 +703,7 @@ static void net_dm_packet_report(struct sk_buff *skb) if (net_dm_trunc_len) payload_len = min_t(size_t, net_dm_trunc_len, payload_len); - msg = nlmsg_new(net_dm_packet_report_size(payload_len, - NET_DM_SKB_CB(skb)->reason), - GFP_KERNEL); + msg = nlmsg_new(net_dm_packet_report_size(payload_len), GFP_KERNEL); if (!msg) goto out; diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 050a875d09c5..62bf5a756258 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -122,11 +122,59 @@ EXPORT_SYMBOL(sysctl_max_skb_frags); #undef FN #define FN(reason) [SKB_DROP_REASON_##reason] = #reason, -const char * const drop_reasons[] = { +static const char * const drop_reasons[] = { [SKB_CONSUMED] = "CONSUMED", DEFINE_DROP_REASON(FN, FN) }; -EXPORT_SYMBOL(drop_reasons); + +static const struct drop_reason_list drop_reasons_core = { + .reasons = drop_reasons, + .n_reasons = ARRAY_SIZE(drop_reasons), +}; + +const struct drop_reason_list __rcu * +drop_reasons_by_subsys[SKB_DROP_REASON_SUBSYS_NUM] = { + [SKB_DROP_REASON_SUBSYS_CORE] = &drop_reasons_core, +}; +EXPORT_SYMBOL(drop_reasons_by_subsys); + +/** + * drop_reasons_register_subsys - register another drop reason subsystem + * @subsys: the subsystem to register, must not be the core + * @list: the list of drop reasons within the subsystem, must point to + * a statically initialized list + */ +void drop_reasons_register_subsys(enum skb_drop_reason_subsys subsys, + const struct drop_reason_list *list) +{ + if (WARN(subsys <= SKB_DROP_REASON_SUBSYS_CORE || + subsys >= ARRAY_SIZE(drop_reasons_by_subsys), + "invalid subsystem %d\n", subsys)) + return; + + /* must point to statically allocated memory, so INIT is OK */ + RCU_INIT_POINTER(drop_reasons_by_subsys[subsys], list); +} +EXPORT_SYMBOL_GPL(drop_reasons_register_subsys); + +/** + * drop_reasons_unregister_subsys - unregister a drop reason subsystem + * @subsys: the subsystem to remove, must not be the core + * + * Note: This will synchronize_rcu() to ensure no users when it returns. + */ +void drop_reasons_unregister_subsys(enum skb_drop_reason_subsys subsys) +{ + if (WARN(subsys <= SKB_DROP_REASON_SUBSYS_CORE || + subsys >= ARRAY_SIZE(drop_reasons_by_subsys), + "invalid subsystem %d\n", subsys)) + return; + + RCU_INIT_POINTER(drop_reasons_by_subsys[subsys], NULL); + + synchronize_rcu(); +} +EXPORT_SYMBOL_GPL(drop_reasons_unregister_subsys); /** * skb_panic - private function for out-of-line support @@ -984,7 +1032,7 @@ bool __kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason) if (unlikely(!skb_unref(skb))) return false; - DEBUG_NET_WARN_ON_ONCE(reason <= 0 || reason >= SKB_DROP_REASON_MAX); + DEBUG_NET_WARN_ON_ONCE(reason == SKB_NOT_DROPPED_YET); if (reason == SKB_CONSUMED) trace_consume_skb(skb, __builtin_return_address(0)); -- 2.39.2
