[PATCH net-next v2] net: sched: cls_api: improve the error message for ID allocation failure
From: Jakub Kicinski <kuba@kernel.org>
Date: 2024-11-08 01:02:56
We run into an exhaustion problem with the kernel-allocated filter IDs. Our allocation problem can be fixed on the user space side, but the error message in this case was quite misleading: "Filter with specified priority/protocol not found" (EINVAL) Specifically when we can't allocate a _new_ ID because filter with lowest ID already _exists_, saying "filter not found", is confusing. Kernel allocates IDs in range of 0xc0000 -> 0x8000, giving out ID one lower than lowest existing in that range. The error message makes sense when tcf_chain_tp_find() gets called for GET and DEL but for NEW we need to provide more specific error messages for all three cases: - user wants the ID to be auto-allocated but filter with ID 0x8000 already exists - filter already exists and can be replaced, but user asked for a protocol change - filter doesn't exist Caller of tcf_chain_tp_insert_unique() doesn't set extack today, so don't bother plumbing it in. Reviewed-by: Simon Horman <horms@kernel.org> Signed-off-by: Jakub Kicinski <kuba@kernel.org> --- v1 was sent a while back, I realized this is sitting in my tree I think I just forgot to send v2. v2: - don't add the extack if we don't find the filter during NEW v1: https://lore.kernel.org/20240912215306.2060709-1-kuba@kernel.org CC: jhs@mojatatu.com CC: xiyou.wangcong@gmail.com CC: jiri@resnulli.us --- net/sched/cls_api.c | 39 +++++++++++++++++++++++++-------------- 1 file changed, 25 insertions(+), 14 deletions(-)
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 2a7d856cc334..5c8d39b6b107 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c@@ -1933,7 +1933,8 @@ static void tcf_chain_tp_remove(struct tcf_chain *chain, static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain, struct tcf_chain_info *chain_info, u32 protocol, u32 prio, - bool prio_allocate); + bool prio_allocate, + struct netlink_ext_ack *extack); /* Try to insert new proto. * If proto with specified priority already exists, free new proto
@@ -1957,8 +1958,7 @@ static struct tcf_proto *tcf_chain_tp_insert_unique(struct tcf_chain *chain, return ERR_PTR(-EAGAIN); } - tp = tcf_chain_tp_find(chain, &chain_info, - protocol, prio, false); + tp = tcf_chain_tp_find(chain, &chain_info, protocol, prio, false, NULL); if (!tp) err = tcf_chain_tp_insert(chain, &chain_info, tp_new); mutex_unlock(&chain->filter_chain_lock);
@@ -2018,7 +2018,8 @@ static void tcf_chain_tp_delete_empty(struct tcf_chain *chain, static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain, struct tcf_chain_info *chain_info, u32 protocol, u32 prio, - bool prio_allocate) + bool prio_allocate, + struct netlink_ext_ack *extack) { struct tcf_proto **pprev; struct tcf_proto *tp;
@@ -2029,9 +2030,14 @@ static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain, pprev = &tp->next) { if (tp->prio >= prio) { if (tp->prio == prio) { - if (prio_allocate || - (tp->protocol != protocol && protocol)) + if (prio_allocate) { + NL_SET_ERR_MSG(extack, "Lowest ID from auto-alloc range already in use"); + return ERR_PTR(-ENOSPC); + } + if (tp->protocol != protocol && protocol) { + NL_SET_ERR_MSG(extack, "Protocol mismatch for filter with specified priority"); return ERR_PTR(-EINVAL); + } } else { tp = NULL; }
@@ -2312,9 +2318,8 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n, mutex_lock(&chain->filter_chain_lock); tp = tcf_chain_tp_find(chain, &chain_info, protocol, - prio, prio_allocate); + prio, prio_allocate, extack); if (IS_ERR(tp)) { - NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found"); err = PTR_ERR(tp); goto errout_locked; }
@@ -2539,10 +2544,13 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n, mutex_lock(&chain->filter_chain_lock); tp = tcf_chain_tp_find(chain, &chain_info, protocol, - prio, false); - if (!tp || IS_ERR(tp)) { + prio, false, extack); + if (!tp) { + err = -ENOENT; NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found"); - err = tp ? PTR_ERR(tp) : -ENOENT; + goto errout_locked; + } else if (IS_ERR(tp)) { + err = PTR_ERR(tp); goto errout_locked; } else if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) { NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
@@ -2679,11 +2687,14 @@ static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n, mutex_lock(&chain->filter_chain_lock); tp = tcf_chain_tp_find(chain, &chain_info, protocol, - prio, false); + prio, false, extack); mutex_unlock(&chain->filter_chain_lock); - if (!tp || IS_ERR(tp)) { + if (!tp) { + err = -ENOENT; NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found"); - err = tp ? PTR_ERR(tp) : -ENOENT; + goto errout; + } else if (IS_ERR(tp)) { + err = PTR_ERR(tp); goto errout; } else if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) { NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
--
2.47.0