diff mbox series

[net-next,2/3] net: icmp: add skb drop reasons to ping_queue_rcv_skb()

Message ID 20220314113225.151959-3-imagedong@tencent.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series net: icmp: add skb drop reasons to icmp | expand

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netdev/tree_selection success Clearly marked for net-next
netdev/fixes_present success Fixes tag not required for -next series
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netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 2 this patch: 2
netdev/cc_maintainers success CCed 5 of 5 maintainers
netdev/build_clang success Errors and warnings before: 18 this patch: 18
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 7 this patch: 7
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 16 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Menglong Dong March 14, 2022, 11:32 a.m. UTC 
From: Menglong Dong <imagedong@tencent.com>

In order to get the reasons of skb drops, replace sock_queue_rcv_skb()
used in ping_queue_rcv_skb() with sock_queue_rcv_skb_reason().
Meanwhile, use kfree_skb_reason() instead of kfree_skb().

As we can see in ping_rcv(), 'skb' will be freed if '-1' is returned
by ping_queue_rcv_skb(). In order to get the drop reason of 'skb',
make ping_queue_rcv_skb() return the drop reason.

As ping_queue_rcv_skb() is used as 'ping_prot.backlog_rcv()', we can't
change its return type. (Seems ping_prot.backlog_rcv() is not used?)
Therefore, make it return 'drop_reason * -1' to keep the origin logic.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
 net/ipv4/ping.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Comments

Paolo Abeni March 15, 2022, 12:49 p.m. UTC | #1 
Hello,

On Mon, 2022-03-14 at 19:32 +0800, menglong8.dong@gmail.com wrote:
> From: Menglong Dong <imagedong@tencent.com>
> 
> In order to get the reasons of skb drops, replace sock_queue_rcv_skb()
> used in ping_queue_rcv_skb() with sock_queue_rcv_skb_reason().
> Meanwhile, use kfree_skb_reason() instead of kfree_skb().
> 
> As we can see in ping_rcv(), 'skb' will be freed if '-1' is returned
> by ping_queue_rcv_skb(). In order to get the drop reason of 'skb',
> make ping_queue_rcv_skb() return the drop reason.
> 
> As ping_queue_rcv_skb() is used as 'ping_prot.backlog_rcv()', we can't
> change its return type. (Seems ping_prot.backlog_rcv() is not used?)
> Therefore, make it return 'drop_reason * -1' to keep the origin logic.
> 
> Signed-off-by: Menglong Dong <imagedong@tencent.com>
> ---
>  net/ipv4/ping.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
> index 3ee947557b88..cd4eb211431a 100644
> --- a/net/ipv4/ping.c
> +++ b/net/ipv4/ping.c
> @@ -936,12 +936,13 @@ EXPORT_SYMBOL_GPL(ping_recvmsg);
>  
>  int ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
>  {
> +	enum skb_drop_reason reason;

Please insert an empty line between variable declaration and code.

>  	pr_debug("ping_queue_rcv_skb(sk=%p,sk->num=%d,skb=%p)\n",
>  		 inet_sk(sk), inet_sk(sk)->inet_num, skb);
> -	if (sock_queue_rcv_skb(sk, skb) < 0) {
> -		kfree_skb(skb);
> +	if (sock_queue_rcv_skb_reason(sk, skb, &reason) < 0) {
> +		kfree_skb_reason(skb, reason);
>  		pr_debug("ping_queue_rcv_skb -> failed\n");
> -		return -1;
> +		return -reason;

This changes the return value for the release callback.  Such callback
has a long and non trivial call chain via sk_backlog_rcv. 

It *should* be safe, but have you considered factoring out an
__ping_queue_rcv_skb() variant returning the full drop reason, use it
in the next patch and build ping_queue_rcv_skb() on top of such helper
to that backlog_rcv() return code will not change?

The above should additionally avoid the IMHO not so nice:

	reason = ping_queue_rcv_skb(sk, skb2) * -1;

in the next patch - it will become:

	reason = __ping_queue_rcv_skb(sk, skb2);

Thanks!

Paolo
Menglong Dong March 16, 2022, 1:34 a.m. UTC | #2 
On Tue, Mar 15, 2022 at 8:49 PM Paolo Abeni <pabeni@redhat.com> wrote:
>
> Hello,
>
> On Mon, 2022-03-14 at 19:32 +0800, menglong8.dong@gmail.com wrote:
> > From: Menglong Dong <imagedong@tencent.com>
> >
> > In order to get the reasons of skb drops, replace sock_queue_rcv_skb()
> > used in ping_queue_rcv_skb() with sock_queue_rcv_skb_reason().
> > Meanwhile, use kfree_skb_reason() instead of kfree_skb().
> >
> > As we can see in ping_rcv(), 'skb' will be freed if '-1' is returned
> > by ping_queue_rcv_skb(). In order to get the drop reason of 'skb',
> > make ping_queue_rcv_skb() return the drop reason.
> >
> > As ping_queue_rcv_skb() is used as 'ping_prot.backlog_rcv()', we can't
> > change its return type. (Seems ping_prot.backlog_rcv() is not used?)
> > Therefore, make it return 'drop_reason * -1' to keep the origin logic.
> >
> > Signed-off-by: Menglong Dong <imagedong@tencent.com>
> > ---
> >  net/ipv4/ping.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
> > index 3ee947557b88..cd4eb211431a 100644
> > --- a/net/ipv4/ping.c
> > +++ b/net/ipv4/ping.c
> > @@ -936,12 +936,13 @@ EXPORT_SYMBOL_GPL(ping_recvmsg);
> >
> >  int ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
> >  {
> > +     enum skb_drop_reason reason;
>
> Please insert an empty line between variable declaration and code.

Ok

>
> >       pr_debug("ping_queue_rcv_skb(sk=%p,sk->num=%d,skb=%p)\n",
> >                inet_sk(sk), inet_sk(sk)->inet_num, skb);
> > -     if (sock_queue_rcv_skb(sk, skb) < 0) {
> > -             kfree_skb(skb);
> > +     if (sock_queue_rcv_skb_reason(sk, skb, &reason) < 0) {
> > +             kfree_skb_reason(skb, reason);
> >               pr_debug("ping_queue_rcv_skb -> failed\n");
> > -             return -1;
> > +             return -reason;
>
> This changes the return value for the release callback.  Such callback
> has a long and non trivial call chain via sk_backlog_rcv.
>
> It *should* be safe, but have you considered factoring out an
> __ping_queue_rcv_skb() variant returning the full drop reason, use it
> in the next patch and build ping_queue_rcv_skb() on top of such helper
> to that backlog_rcv() return code will not change?
>
> The above should additionally avoid the IMHO not so nice:
>
>         reason = ping_queue_rcv_skb(sk, skb2) * -1;
>
> in the next patch - it will become:
>
>         reason = __ping_queue_rcv_skb(sk, skb2);
>

Good idea, thanks!

Menglong Dong
diff mbox series

Patch

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index 3ee947557b88..cd4eb211431a 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -936,12 +936,13 @@  EXPORT_SYMBOL_GPL(ping_recvmsg);
 
 int ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
+	enum skb_drop_reason reason;
 	pr_debug("ping_queue_rcv_skb(sk=%p,sk->num=%d,skb=%p)\n",
 		 inet_sk(sk), inet_sk(sk)->inet_num, skb);
-	if (sock_queue_rcv_skb(sk, skb) < 0) {
-		kfree_skb(skb);
+	if (sock_queue_rcv_skb_reason(sk, skb, &reason) < 0) {
+		kfree_skb_reason(skb, reason);
 		pr_debug("ping_queue_rcv_skb -> failed\n");
-		return -1;
+		return -reason;
 	}
 	return 0;
 }