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net: sched: cls_api: improve the error message for ID allocation failure

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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>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/20241108010254.2995438-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Jakub Kicinski 2024-11-07 17:02:54 -08:00 committed by Paolo Abeni
parent 12079a59ce
commit a58f00ed24
1 changed files with 25 additions and 14 deletions
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39
net/sched/cls_api.c
View File

@ -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");