Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap

Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap

[zhudi (E)]

> On 11/2/21 1:48 AM, Di Zhu wrote:
> > Right now there is no way to query whether BPF programs are
> > attached to a sockmap or not.
> >
> > we can use the standard interface in libbpf to query, such as:
> > bpf_prog_query(mapFd, BPF_SK_SKB_STREAM_PARSER, 0, NULL, ...);
> > the mapFd is the fd of sockmap.
> >
> > Signed-off-by: Di Zhu <zhudi2@huawei.com>
> > ---
> >   include/linux/bpf.h  |  9 +++++
> >   kernel/bpf/syscall.c |  5 +++
> >   net/core/sock_map.c  | 88
> ++++++++++++++++++++++++++++++++++++++++----
> >   3 files changed, 95 insertions(+), 7 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index d604c8251d88..594ca91992db 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -1961,6 +1961,9 @@ int bpf_prog_test_run_syscall(struct bpf_prog
> *prog,
> >   int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog
> *prog);
> >   int sock_map_prog_detach(const union bpf_attr *attr, enum
> bpf_prog_type ptype);
> >   int sock_map_update_elem_sys(struct bpf_map *map, void *key, void
> *value, u64 flags);
> > +int sockmap_bpf_prog_query(const union bpf_attr *attr,
> > +			   union bpf_attr __user *uattr);
> 
> All previous functions are with prefix "sock_map". Why you choose
> a different prefix "sockmap"?
> 

Thanks for all your suggestions, I will make changes to the inappropriate code.

> > +
> >   void sock_map_unhash(struct sock *sk);
> >   void sock_map_close(struct sock *sk, long timeout);
> >   #else
> > @@ -2014,6 +2017,12 @@ static inline int
> sock_map_update_elem_sys(struct bpf_map *map, void *key, void
> >   {
> >   	return -EOPNOTSUPP;
> >   }
> > +
> > +static inline int sockmap_bpf_prog_query(const union bpf_attr *attr,
> > +					 union bpf_attr __user *uattr)
> > +{
> > +	return -EINVAL;
> > +}
> >   #endif /* CONFIG_BPF_SYSCALL */
> >   #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
> >
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index 4e50c0bfdb7d..17faeff8f85f 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -3275,6 +3275,11 @@ static int bpf_prog_query(const union bpf_attr
> *attr,
> >   	case BPF_FLOW_DISSECTOR:
> >   	case BPF_SK_LOOKUP:
> >   		return netns_bpf_prog_query(attr, uattr);
> > +	case BPF_SK_SKB_STREAM_PARSER:
> > +	case BPF_SK_SKB_STREAM_VERDICT:
> > +	case BPF_SK_MSG_VERDICT:
> > +	case BPF_SK_SKB_VERDICT:
> > +		return sockmap_bpf_prog_query(attr, uattr);
> >   	default:
> >   		return -EINVAL;
> >   	}
> > diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> > index e252b8ec2b85..ca65ed0004d3 100644
> > --- a/net/core/sock_map.c
> > +++ b/net/core/sock_map.c
> > @@ -1412,38 +1412,50 @@ static struct sk_psock_progs
> *sock_map_progs(struct bpf_map *map)
> >   	return NULL;
> >   }
> >
> > -static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog
> *prog,
> > -				struct bpf_prog *old, u32 which)
> > +static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog
> **pprog[],
> 
> Can we just change "**pprog[]" to "***pprog"? In the code, you really
> just pass the address of the decl "struct bpf_prog **pprog;" to the
> function.
> 
> > +				u32 which)
> 
> Some format issue here?


Format is right, passed the checkpatch script check.


> 
> >   {
> >   	struct sk_psock_progs *progs = sock_map_progs(map);
> > -	struct bpf_prog **pprog;
> >
> >   	if (!progs)
> >   		return -EOPNOTSUPP;
> >
> >   	switch (which) {
> >   	case BPF_SK_MSG_VERDICT:
> > -		pprog = &progs->msg_parser;
> > +		*pprog = &progs->msg_parser;
> >   		break;
> >   #if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
> >   	case BPF_SK_SKB_STREAM_PARSER:
> > -		pprog = &progs->stream_parser;
> > +		*pprog = &progs->stream_parser;
> >   		break;
> >   #endif
> >   	case BPF_SK_SKB_STREAM_VERDICT:
> >   		if (progs->skb_verdict)
> >   			return -EBUSY;
> > -		pprog = &progs->stream_verdict;
> > +		*pprog = &progs->stream_verdict;
> >   		break;
> >   	case BPF_SK_SKB_VERDICT:
> >   		if (progs->stream_verdict)
> >   			return -EBUSY;
> > -		pprog = &progs->skb_verdict;
> > +		*pprog = &progs->skb_verdict;
> >   		break;
> >   	default:
> >   		return -EOPNOTSUPP;
> >   	}
> >
> > +	return 0;
> > +}
> > +
> > +static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog
> *prog,
> > +				struct bpf_prog *old, u32 which)
> 
> Some format issue here?
> 
> > +{
> > +	struct bpf_prog **pprog;
> > +	int ret;
> > +
> > +	ret = sock_map_prog_lookup(map, &pprog, which);
> > +	if (ret)
> > +		return ret;
> > +
> >   	if (old)
> >   		return psock_replace_prog(pprog, prog, old);
> >
> > @@ -1451,6 +1463,68 @@ static int sock_map_prog_update(struct
> bpf_map *map, struct bpf_prog *prog,
> >   	return 0;
> >   }
> >
> > +int sockmap_bpf_prog_query(const union bpf_attr *attr,
> > +			   union bpf_attr __user *uattr)
> 
> Format issue here?
> 
> > +{
> > +	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
> 
> Typically we use u32 in the kernel code. But I know there are __u32
> usage as well, esp. with __user attributes. I put a comment here just
> in case that somebody else has a different opinion.
> 
> > +	u32 prog_cnt = 0, flags = 0;
> > +	u32 ufd = attr->target_fd;
> 
> You can merge the above u32 together.
> 
> > +	struct bpf_prog **pprog;
> > +	struct bpf_prog *prog;
> > +	struct bpf_map *map;
> > +	struct fd f;
> > +	int ret;
> > +	u32 id = 0;
> 
> to maintain reverse christmas tree?
> 
> > +
> > +	if (attr->query.query_flags)
> > +		return -EINVAL;
> > +
> > +	f = fdget(ufd);
> > +	map = __bpf_map_get(f);
> > +	if (IS_ERR(map))
> > +		return PTR_ERR(map);
> > +
> > +	rcu_read_lock();
> > +
> > +	ret = sock_map_prog_lookup(map, &pprog, attr->query.attach_type);
> > +	if (ret)
> > +		goto end;
> > +
> > +	prog = *pprog;
> > +	prog_cnt = (!prog) ? 0 : 1;
> > +
> > +	if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
> > +		goto end;
> > +
> > +	prog = bpf_prog_inc_not_zero(prog);
> 
> Could you explain why we need bpf_prog_inc_not_zero here?
> We are inside rcu_read_lock/unlock region. We got a program
> from *pprog. If this program is not NULL, this program should
> not disappear since we are in rcu read lock region, right?
> Maybe I missed something, it would be good you can explain
> the scenario you try to pretect here.


bpf_prog_inc_not_zero() return a failure indicating that the program is
being released and prog->aux->id will be set to 0.
Yes, it is just ok for accessing prog->aux->id directly.


> > +	if (IS_ERR(prog)) {
> > +		ret = PTR_ERR(prog);
> > +		goto end;
> > +	}
> > +	id = prog->aux->id;
> > +	bpf_prog_put(prog);
> > +
> > +end:
> > +	rcu_read_unlock();
> > +
> > +	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags))) {
> > +		ret = -EFAULT;
> > +		goto err;
> > +	}
> > +	if (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) {
> > +		ret = -EFAULT;
> > +		goto err;
> > +	}
> > +	if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt))) {
> > +		ret = -EFAULT;
> > +		goto err;
> > +	}
> 
> You can do
> 
> 	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)) ||
> 	    (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) ||
> 	    copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
> 		ret = -EFAULT;
> 
> to make code a little bit concise.
> 
> > +
> > +err:
> > +	fdput(f);
> > +	return ret;
> > +}
> > +
> >   static void sock_map_unlink(struct sock *sk, struct sk_psock_link *link)
> >   {
> >   	switch (link->map->map_type) {
> >

Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap

[Yonghong Song]

On 11/2/21 7:23 PM, zhudi (E) wrote:
>> On 11/2/21 1:48 AM, Di Zhu wrote:
>>> Right now there is no way to query whether BPF programs are
>>> attached to a sockmap or not.
>>>
>>> we can use the standard interface in libbpf to query, such as:
>>> bpf_prog_query(mapFd, BPF_SK_SKB_STREAM_PARSER, 0, NULL, ...);
>>> the mapFd is the fd of sockmap.
>>>
>>> Signed-off-by: Di Zhu <zhudi2@huawei.com>
>>> ---
>>>    include/linux/bpf.h  |  9 +++++
>>>    kernel/bpf/syscall.c |  5 +++
>>>    net/core/sock_map.c  | 88
>> ++++++++++++++++++++++++++++++++++++++++----
>>>    3 files changed, 95 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>>> index d604c8251d88..594ca91992db 100644
>>> --- a/include/linux/bpf.h
>>> +++ b/include/linux/bpf.h
>>> @@ -1961,6 +1961,9 @@ int bpf_prog_test_run_syscall(struct bpf_prog
>> *prog,
>>>    int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog
>> *prog);
>>>    int sock_map_prog_detach(const union bpf_attr *attr, enum
>> bpf_prog_type ptype);
>>>    int sock_map_update_elem_sys(struct bpf_map *map, void *key, void
>> *value, u64 flags);
>>> +int sockmap_bpf_prog_query(const union bpf_attr *attr,
>>> +			   union bpf_attr __user *uattr);
>>
>> All previous functions are with prefix "sock_map". Why you choose
>> a different prefix "sockmap"?
>>
> 
> Thanks for all your suggestions, I will make changes to the inappropriate code.
> 
>>> +
>>>    void sock_map_unhash(struct sock *sk);
>>>    void sock_map_close(struct sock *sk, long timeout);
>>>    #else
>>> @@ -2014,6 +2017,12 @@ static inline int
>> sock_map_update_elem_sys(struct bpf_map *map, void *key, void
>>>    {
>>>    	return -EOPNOTSUPP;
>>>    }
>>> +
>>> +static inline int sockmap_bpf_prog_query(const union bpf_attr *attr,
>>> +					 union bpf_attr __user *uattr)
>>> +{
>>> +	return -EINVAL;
>>> +}
>>>    #endif /* CONFIG_BPF_SYSCALL */
>>>    #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
>>>
>>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>>> index 4e50c0bfdb7d..17faeff8f85f 100644
>>> --- a/kernel/bpf/syscall.c
>>> +++ b/kernel/bpf/syscall.c
>>> @@ -3275,6 +3275,11 @@ static int bpf_prog_query(const union bpf_attr
>> *attr,
>>>    	case BPF_FLOW_DISSECTOR:
>>>    	case BPF_SK_LOOKUP:
>>>    		return netns_bpf_prog_query(attr, uattr);
>>> +	case BPF_SK_SKB_STREAM_PARSER:
>>> +	case BPF_SK_SKB_STREAM_VERDICT:
>>> +	case BPF_SK_MSG_VERDICT:
>>> +	case BPF_SK_SKB_VERDICT:
>>> +		return sockmap_bpf_prog_query(attr, uattr);
>>>    	default:
>>>    		return -EINVAL;
>>>    	}
>>> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
>>> index e252b8ec2b85..ca65ed0004d3 100644
>>> --- a/net/core/sock_map.c
>>> +++ b/net/core/sock_map.c
>>> @@ -1412,38 +1412,50 @@ static struct sk_psock_progs
>> *sock_map_progs(struct bpf_map *map)
>>>    	return NULL;
>>>    }
>>>
>>> -static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog
>> *prog,
>>> -				struct bpf_prog *old, u32 which)
>>> +static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog
>> **pprog[],
>>
>> Can we just change "**pprog[]" to "***pprog"? In the code, you really
>> just pass the address of the decl "struct bpf_prog **pprog;" to the
>> function.
>>
>>> +				u32 which)
>>
>> Some format issue here?
> 
> 
> Format is right, passed the checkpatch script check.

Sorry about this. I guess my reply formating cheated me:

 >>> +static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog
 >> **pprog[],
 >>> +				u32 which)

I see a larger misalignment between "struct bpf_map *map" and
"u32 which" in the reply email. But looking at original
patch, there are no issues.

> 
> 
>>
>>>    {
>>>    	struct sk_psock_progs *progs = sock_map_progs(map);
>>> -	struct bpf_prog **pprog;
>>>
>>>    	if (!progs)
>>>    		return -EOPNOTSUPP;
[...]

Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap

[zhudi (E)]

> On Tue, Nov 2, 2021 at 1:11 PM Yonghong Song <yhs@fb.com> wrote:
> > >
> > > -static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog
> *prog,
> > > -                             struct bpf_prog *old, u32 which)
> > > +static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog
> **pprog[],
> >
> > Can we just change "**pprog[]" to "***pprog"? In the code, you really
> > just pass the address of the decl "struct bpf_prog **pprog;" to the
> > function.
> 
> Di,
> 
> this feedback was given twice already.
> You also didn't address several other points from the earlier reviews.
> Please do not resubmit until you address all points.

Maybe i miss something...
I will recheck the review comments.

[PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap

[Di Zhu]

Right now there is no way to query whether BPF programs are
attached to a sockmap or not.

we can use the standard interface in libbpf to query, such as:
bpf_prog_query(mapFd, BPF_SK_SKB_STREAM_PARSER, 0, NULL, ...);
the mapFd is the fd of sockmap.

Signed-off-by: Di Zhu <zhudi2@huawei.com>
---
 include/linux/bpf.h  |  9 +++++
 kernel/bpf/syscall.c |  5 +++
 net/core/sock_map.c  | 88 ++++++++++++++++++++++++++++++++++++++++----
 3 files changed, 95 insertions(+), 7 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d604c8251d88..594ca91992db 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1961,6 +1961,9 @@ int bpf_prog_test_run_syscall(struct bpf_prog *prog,
 int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog);
 int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
 int sock_map_update_elem_sys(struct bpf_map *map, void *key, void *value, u64 flags);
+int sockmap_bpf_prog_query(const union bpf_attr *attr,
+			   union bpf_attr __user *uattr);
+
 void sock_map_unhash(struct sock *sk);
 void sock_map_close(struct sock *sk, long timeout);
 #else
@@ -2014,6 +2017,12 @@ static inline int sock_map_update_elem_sys(struct bpf_map *map, void *key, void
 {
 	return -EOPNOTSUPP;
 }
+
+static inline int sockmap_bpf_prog_query(const union bpf_attr *attr,
+					 union bpf_attr __user *uattr)
+{
+	return -EINVAL;
+}
 #endif /* CONFIG_BPF_SYSCALL */
 #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e50c0bfdb7d..17faeff8f85f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3275,6 +3275,11 @@ static int bpf_prog_query(const union bpf_attr *attr,
 	case BPF_FLOW_DISSECTOR:
 	case BPF_SK_LOOKUP:
 		return netns_bpf_prog_query(attr, uattr);
+	case BPF_SK_SKB_STREAM_PARSER:
+	case BPF_SK_SKB_STREAM_VERDICT:
+	case BPF_SK_MSG_VERDICT:
+	case BPF_SK_SKB_VERDICT:
+		return sockmap_bpf_prog_query(attr, uattr);
 	default:
 		return -EINVAL;
 	}
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index e252b8ec2b85..ca65ed0004d3 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -1412,38 +1412,50 @@ static struct sk_psock_progs *sock_map_progs(struct bpf_map *map)
 	return NULL;
 }
 
-static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
-				struct bpf_prog *old, u32 which)
+static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog **pprog[],
+				u32 which)
 {
 	struct sk_psock_progs *progs = sock_map_progs(map);
-	struct bpf_prog **pprog;
 
 	if (!progs)
 		return -EOPNOTSUPP;
 
 	switch (which) {
 	case BPF_SK_MSG_VERDICT:
-		pprog = &progs->msg_parser;
+		*pprog = &progs->msg_parser;
 		break;
 #if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
 	case BPF_SK_SKB_STREAM_PARSER:
-		pprog = &progs->stream_parser;
+		*pprog = &progs->stream_parser;
 		break;
 #endif
 	case BPF_SK_SKB_STREAM_VERDICT:
 		if (progs->skb_verdict)
 			return -EBUSY;
-		pprog = &progs->stream_verdict;
+		*pprog = &progs->stream_verdict;
 		break;
 	case BPF_SK_SKB_VERDICT:
 		if (progs->stream_verdict)
 			return -EBUSY;
-		pprog = &progs->skb_verdict;
+		*pprog = &progs->skb_verdict;
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}
 
+	return 0;
+}
+
+static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
+				struct bpf_prog *old, u32 which)
+{
+	struct bpf_prog **pprog;
+	int ret;
+
+	ret = sock_map_prog_lookup(map, &pprog, which);
+	if (ret)
+		return ret;
+
 	if (old)
 		return psock_replace_prog(pprog, prog, old);
 
@@ -1451,6 +1463,68 @@ static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
 	return 0;
 }
 
+int sockmap_bpf_prog_query(const union bpf_attr *attr,
+			   union bpf_attr __user *uattr)
+{
+	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
+	u32 prog_cnt = 0, flags = 0;
+	u32 ufd = attr->target_fd;
+	struct bpf_prog **pprog;
+	struct bpf_prog *prog;
+	struct bpf_map *map;
+	struct fd f;
+	int ret;
+	u32 id = 0;
+
+	if (attr->query.query_flags)
+		return -EINVAL;
+
+	f = fdget(ufd);
+	map = __bpf_map_get(f);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	rcu_read_lock();
+
+	ret = sock_map_prog_lookup(map, &pprog, attr->query.attach_type);
+	if (ret)
+		goto end;
+
+	prog = *pprog;
+	prog_cnt = (!prog) ? 0 : 1;
+
+	if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
+		goto end;
+
+	prog = bpf_prog_inc_not_zero(prog);
+	if (IS_ERR(prog)) {
+		ret = PTR_ERR(prog);
+		goto end;
+	}
+	id = prog->aux->id;
+	bpf_prog_put(prog);
+
+end:
+	rcu_read_unlock();
+
+	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags))) {
+		ret = -EFAULT;
+		goto err;
+	}
+	if (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) {
+		ret = -EFAULT;
+		goto err;
+	}
+	if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt))) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+err:
+	fdput(f);
+	return ret;
+}
+
 static void sock_map_unlink(struct sock *sk, struct sk_psock_link *link)
 {
 	switch (link->map->map_type) {
-- 
2.27.0

Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap

[Yonghong Song]

On 11/2/21 1:48 AM, Di Zhu wrote:
> Right now there is no way to query whether BPF programs are
> attached to a sockmap or not.
> 
> we can use the standard interface in libbpf to query, such as:
> bpf_prog_query(mapFd, BPF_SK_SKB_STREAM_PARSER, 0, NULL, ...);
> the mapFd is the fd of sockmap.
> 
> Signed-off-by: Di Zhu <zhudi2@huawei.com>
> ---
>   include/linux/bpf.h  |  9 +++++
>   kernel/bpf/syscall.c |  5 +++
>   net/core/sock_map.c  | 88 ++++++++++++++++++++++++++++++++++++++++----
>   3 files changed, 95 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index d604c8251d88..594ca91992db 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1961,6 +1961,9 @@ int bpf_prog_test_run_syscall(struct bpf_prog *prog,
>   int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog);
>   int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
>   int sock_map_update_elem_sys(struct bpf_map *map, void *key, void *value, u64 flags);
> +int sockmap_bpf_prog_query(const union bpf_attr *attr,
> +			   union bpf_attr __user *uattr);

All previous functions are with prefix "sock_map". Why you choose
a different prefix "sockmap"?

> +
>   void sock_map_unhash(struct sock *sk);
>   void sock_map_close(struct sock *sk, long timeout);
>   #else
> @@ -2014,6 +2017,12 @@ static inline int sock_map_update_elem_sys(struct bpf_map *map, void *key, void
>   {
>   	return -EOPNOTSUPP;
>   }
> +
> +static inline int sockmap_bpf_prog_query(const union bpf_attr *attr,
> +					 union bpf_attr __user *uattr)
> +{
> +	return -EINVAL;
> +}
>   #endif /* CONFIG_BPF_SYSCALL */
>   #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
>   
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 4e50c0bfdb7d..17faeff8f85f 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3275,6 +3275,11 @@ static int bpf_prog_query(const union bpf_attr *attr,
>   	case BPF_FLOW_DISSECTOR:
>   	case BPF_SK_LOOKUP:
>   		return netns_bpf_prog_query(attr, uattr);
> +	case BPF_SK_SKB_STREAM_PARSER:
> +	case BPF_SK_SKB_STREAM_VERDICT:
> +	case BPF_SK_MSG_VERDICT:
> +	case BPF_SK_SKB_VERDICT:
> +		return sockmap_bpf_prog_query(attr, uattr);
>   	default:
>   		return -EINVAL;
>   	}
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index e252b8ec2b85..ca65ed0004d3 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -1412,38 +1412,50 @@ static struct sk_psock_progs *sock_map_progs(struct bpf_map *map)
>   	return NULL;
>   }
>   
> -static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
> -				struct bpf_prog *old, u32 which)
> +static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog **pprog[],

Can we just change "**pprog[]" to "***pprog"? In the code, you really 
just pass the address of the decl "struct bpf_prog **pprog;" to the 
function.

> +				u32 which)

Some format issue here?

>   {
>   	struct sk_psock_progs *progs = sock_map_progs(map);
> -	struct bpf_prog **pprog;
>   
>   	if (!progs)
>   		return -EOPNOTSUPP;
>   
>   	switch (which) {
>   	case BPF_SK_MSG_VERDICT:
> -		pprog = &progs->msg_parser;
> +		*pprog = &progs->msg_parser;
>   		break;
>   #if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
>   	case BPF_SK_SKB_STREAM_PARSER:
> -		pprog = &progs->stream_parser;
> +		*pprog = &progs->stream_parser;
>   		break;
>   #endif
>   	case BPF_SK_SKB_STREAM_VERDICT:
>   		if (progs->skb_verdict)
>   			return -EBUSY;
> -		pprog = &progs->stream_verdict;
> +		*pprog = &progs->stream_verdict;
>   		break;
>   	case BPF_SK_SKB_VERDICT:
>   		if (progs->stream_verdict)
>   			return -EBUSY;
> -		pprog = &progs->skb_verdict;
> +		*pprog = &progs->skb_verdict;
>   		break;
>   	default:
>   		return -EOPNOTSUPP;
>   	}
>   
> +	return 0;
> +}
> +
> +static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
> +				struct bpf_prog *old, u32 which)

Some format issue here?

> +{
> +	struct bpf_prog **pprog;
> +	int ret;
> +
> +	ret = sock_map_prog_lookup(map, &pprog, which);
> +	if (ret)
> +		return ret;
> +
>   	if (old)
>   		return psock_replace_prog(pprog, prog, old);
>   
> @@ -1451,6 +1463,68 @@ static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
>   	return 0;
>   }
>   
> +int sockmap_bpf_prog_query(const union bpf_attr *attr,
> +			   union bpf_attr __user *uattr)

Format issue here?

> +{
> +	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);

Typically we use u32 in the kernel code. But I know there are __u32 
usage as well, esp. with __user attributes. I put a comment here just
in case that somebody else has a different opinion.

> +	u32 prog_cnt = 0, flags = 0;
> +	u32 ufd = attr->target_fd;

You can merge the above u32 together.

> +	struct bpf_prog **pprog;
> +	struct bpf_prog *prog;
> +	struct bpf_map *map;
> +	struct fd f;
> +	int ret;
> +	u32 id = 0;

to maintain reverse christmas tree?

> +
> +	if (attr->query.query_flags)
> +		return -EINVAL;
> +
> +	f = fdget(ufd);
> +	map = __bpf_map_get(f);
> +	if (IS_ERR(map))
> +		return PTR_ERR(map);
> +
> +	rcu_read_lock();
> +
> +	ret = sock_map_prog_lookup(map, &pprog, attr->query.attach_type);
> +	if (ret)
> +		goto end;
> +
> +	prog = *pprog;
> +	prog_cnt = (!prog) ? 0 : 1;
> +
> +	if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
> +		goto end;
> +
> +	prog = bpf_prog_inc_not_zero(prog);

Could you explain why we need bpf_prog_inc_not_zero here?
We are inside rcu_read_lock/unlock region. We got a program
from *pprog. If this program is not NULL, this program should
not disappear since we are in rcu read lock region, right?
Maybe I missed something, it would be good you can explain
the scenario you try to pretect here.

> +	if (IS_ERR(prog)) {
> +		ret = PTR_ERR(prog);
> +		goto end;
> +	}
> +	id = prog->aux->id;
> +	bpf_prog_put(prog);
> +
> +end:
> +	rcu_read_unlock();
> +
> +	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags))) {
> +		ret = -EFAULT;
> +		goto err;
> +	}
> +	if (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) {
> +		ret = -EFAULT;
> +		goto err;
> +	}
> +	if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt))) {
> +		ret = -EFAULT;
> +		goto err;
> +	}

You can do

	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)) ||
	    (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) ||
	    copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
		ret = -EFAULT;

to make code a little bit concise.

> +
> +err:
> +	fdput(f);
> +	return ret;
> +}
> +
>   static void sock_map_unlink(struct sock *sk, struct sk_psock_link *link)
>   {
>   	switch (link->map->map_type) {
> 

Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap

[Alexei Starovoitov]

On Tue, Nov 2, 2021 at 1:11 PM Yonghong Song <yhs@fb.com> wrote:
> >
> > -static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
> > -                             struct bpf_prog *old, u32 which)
> > +static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog **pprog[],
>
> Can we just change "**pprog[]" to "***pprog"? In the code, you really
> just pass the address of the decl "struct bpf_prog **pprog;" to the
> function.

Di,

this feedback was given twice already.
You also didn't address several other points from the earlier reviews.
Please do not resubmit until you address all points.

[PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap

[Di Zhu]

Right now there is no way to query whether BPF programs are
attached to a sockmap or not.

we can use the standard interface in libbpf to query, such as:
bpf_prog_query(mapFd, BPF_SK_SKB_STREAM_PARSER, 0, NULL, ...);
the mapFd is the fd of sockmap.

Signed-off-by: Di Zhu <zhudi2@huawei.com>
---
 include/linux/bpf.h  |  9 +++++
 kernel/bpf/syscall.c |  5 +++
 net/core/sock_map.c  | 88 ++++++++++++++++++++++++++++++++++++++++----
 3 files changed, 95 insertions(+), 7 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d604c8251d88..db7d0e5115b7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1961,6 +1961,9 @@ int bpf_prog_test_run_syscall(struct bpf_prog *prog,
 int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog);
 int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
 int sock_map_update_elem_sys(struct bpf_map *map, void *key, void *value, u64 flags);
+int sockmap_bpf_prog_query(const union bpf_attr *attr,
+				 union bpf_attr __user *uattr);
+
 void sock_map_unhash(struct sock *sk);
 void sock_map_close(struct sock *sk, long timeout);
 #else
@@ -2014,6 +2017,12 @@ static inline int sock_map_update_elem_sys(struct bpf_map *map, void *key, void
 {
 	return -EOPNOTSUPP;
 }
+
+static inline int sockmap_bpf_prog_query(const union bpf_attr *attr,
+					       union bpf_attr __user *uattr)
+{
+	return -EINVAL;
+}
 #endif /* CONFIG_BPF_SYSCALL */
 #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e50c0bfdb7d..17faeff8f85f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3275,6 +3275,11 @@ static int bpf_prog_query(const union bpf_attr *attr,
 	case BPF_FLOW_DISSECTOR:
 	case BPF_SK_LOOKUP:
 		return netns_bpf_prog_query(attr, uattr);
+	case BPF_SK_SKB_STREAM_PARSER:
+	case BPF_SK_SKB_STREAM_VERDICT:
+	case BPF_SK_MSG_VERDICT:
+	case BPF_SK_SKB_VERDICT:
+		return sockmap_bpf_prog_query(attr, uattr);
 	default:
 		return -EINVAL;
 	}
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index e252b8ec2b85..ca65ed0004d3 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -1412,38 +1412,50 @@ static struct sk_psock_progs *sock_map_progs(struct bpf_map *map)
 	return NULL;
 }
 
-static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
-				struct bpf_prog *old, u32 which)
+static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog **pprog[],
+				u32 which)
 {
 	struct sk_psock_progs *progs = sock_map_progs(map);
-	struct bpf_prog **pprog;
 
 	if (!progs)
 		return -EOPNOTSUPP;
 
 	switch (which) {
 	case BPF_SK_MSG_VERDICT:
-		pprog = &progs->msg_parser;
+		*pprog = &progs->msg_parser;
 		break;
 #if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
 	case BPF_SK_SKB_STREAM_PARSER:
-		pprog = &progs->stream_parser;
+		*pprog = &progs->stream_parser;
 		break;
 #endif
 	case BPF_SK_SKB_STREAM_VERDICT:
 		if (progs->skb_verdict)
 			return -EBUSY;
-		pprog = &progs->stream_verdict;
+		*pprog = &progs->stream_verdict;
 		break;
 	case BPF_SK_SKB_VERDICT:
 		if (progs->stream_verdict)
 			return -EBUSY;
-		pprog = &progs->skb_verdict;
+		*pprog = &progs->skb_verdict;
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}
 
+	return 0;
+}
+
+static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
+				struct bpf_prog *old, u32 which)
+{
+	struct bpf_prog **pprog;
+	int ret;
+
+	ret = sock_map_prog_lookup(map, &pprog, which);
+	if (ret)
+		return ret;
+
 	if (old)
 		return psock_replace_prog(pprog, prog, old);
 
@@ -1451,6 +1463,68 @@ static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
 	return 0;
 }
 
+int sockmap_bpf_prog_query(const union bpf_attr *attr,
+			   union bpf_attr __user *uattr)
+{
+	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
+	u32 prog_cnt = 0, flags = 0;
+	u32 ufd = attr->target_fd;
+	struct bpf_prog **pprog;
+	struct bpf_prog *prog;
+	struct bpf_map *map;
+	struct fd f;
+	int ret;
+	u32 id = 0;
+
+	if (attr->query.query_flags)
+		return -EINVAL;
+
+	f = fdget(ufd);
+	map = __bpf_map_get(f);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	rcu_read_lock();
+
+	ret = sock_map_prog_lookup(map, &pprog, attr->query.attach_type);
+	if (ret)
+		goto end;
+
+	prog = *pprog;
+	prog_cnt = (!prog) ? 0 : 1;
+
+	if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
+		goto end;
+
+	prog = bpf_prog_inc_not_zero(prog);
+	if (IS_ERR(prog)) {
+		ret = PTR_ERR(prog);
+		goto end;
+	}
+	id = prog->aux->id;
+	bpf_prog_put(prog);
+
+end:
+	rcu_read_unlock();
+
+	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags))) {
+		ret = -EFAULT;
+		goto err;
+	}
+	if (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) {
+		ret = -EFAULT;
+		goto err;
+	}
+	if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt))) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+err:
+	fdput(f);
+	return ret;
+}
+
 static void sock_map_unlink(struct sock *sk, struct sk_psock_link *link)
 {
 	switch (link->map->map_type) {
-- 
2.27.0