[PATCH net-next] ppp: simplify input error handling

[PATCH net-next] ppp: simplify input error handling

[Qingfang Deng]

Currently, ppp_input_error() indicates an error by allocating a 0-length
skb and calling ppp_do_recv(). It takes an error code argument, which is
stored in skb->cb, but not used by ppp_receive_frame().

Simplify the error handling by removing the unused parameter and the
unnecessary skb allocation. Instead, call ppp_receive_error() directly
from ppp_input_error() under the recv lock, and the length check in
ppp_receive_frame() can be removed.

Signed-off-by: Qingfang Deng <dqfext@gmail.com>
---
 drivers/net/ppp/ppp_async.c   |  2 +-
 drivers/net/ppp/ppp_generic.c | 31 ++++++++++---------------------
 drivers/net/ppp/ppp_synctty.c |  2 +-
 include/linux/ppp_channel.h   |  2 +-
 net/atm/pppoatm.c             |  2 +-
 5 files changed, 14 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ppp/ppp_async.c b/drivers/net/ppp/ppp_async.c
index b4cf2d09c6bd..93a7b0f6c4e7 100644
--- a/drivers/net/ppp/ppp_async.c
+++ b/drivers/net/ppp/ppp_async.c
@@ -491,7 +491,7 @@ static void ppp_async_process(struct tasklet_struct *t)
 	/* process received packets */
 	while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
 		if (skb->cb[0])
-			ppp_input_error(&ap->chan, 0);
+			ppp_input_error(&ap->chan);
 		ppp_input(&ap->chan, skb);
 	}
 
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 2081da6c2144..6344c5eb0f98 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -2383,12 +2383,10 @@ ppp_input(struct ppp_channel *chan, struct sk_buff *skb)
 	rcu_read_unlock_bh();
 }
 
-/* Put a 0-length skb in the receive queue as an error indication */
 void
-ppp_input_error(struct ppp_channel *chan, int code)
+ppp_input_error(struct ppp_channel *chan)
 {
 	struct channel *pch = chan->ppp;
-	struct sk_buff *skb;
 	struct ppp *ppp;
 
 	if (!pch)
@@ -2397,12 +2395,9 @@ ppp_input_error(struct ppp_channel *chan, int code)
 	rcu_read_lock_bh();
 	ppp = rcu_dereference_bh(pch->ppp);
 	if (ppp) {
-		skb = alloc_skb(0, GFP_ATOMIC);
-		if (skb) {
-			skb->len = 0;		/* probably unnecessary */
-			skb->cb[0] = code;
-			ppp_do_recv(ppp, skb, pch);
-		}
+		ppp_recv_lock(ppp);
+		ppp_receive_error(ppp);
+		ppp_recv_unlock(ppp);
 	}
 	rcu_read_unlock_bh();
 }
@@ -2414,20 +2409,14 @@ ppp_input_error(struct ppp_channel *chan, int code)
 static void
 ppp_receive_frame(struct ppp *ppp, struct sk_buff *skb, struct channel *pch)
 {
-	/* note: a 0-length skb is used as an error indication */
-	if (skb->len > 0) {
-		skb_checksum_complete_unset(skb);
+	skb_checksum_complete_unset(skb);
 #ifdef CONFIG_PPP_MULTILINK
-		/* XXX do channel-level decompression here */
-		if (PPP_PROTO(skb) == PPP_MP)
-			ppp_receive_mp_frame(ppp, skb, pch);
-		else
+	/* XXX do channel-level decompression here */
+	if (PPP_PROTO(skb) == PPP_MP)
+		ppp_receive_mp_frame(ppp, skb, pch);
+	else
 #endif /* CONFIG_PPP_MULTILINK */
-			ppp_receive_nonmp_frame(ppp, skb);
-	} else {
-		kfree_skb(skb);
-		ppp_receive_error(ppp);
-	}
+		ppp_receive_nonmp_frame(ppp, skb);
 }
 
 static void
diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c
index c2063961f395..b7f243b416f8 100644
--- a/drivers/net/ppp/ppp_synctty.c
+++ b/drivers/net/ppp/ppp_synctty.c
@@ -483,7 +483,7 @@ static void ppp_sync_process(struct tasklet_struct *t)
 	while ((skb = skb_dequeue(&ap->rqueue)) != NULL) {
 		if (skb->len == 0) {
 			/* zero length buffers indicate error */
-			ppp_input_error(&ap->chan, 0);
+			ppp_input_error(&ap->chan);
 			kfree_skb(skb);
 		}
 		else
diff --git a/include/linux/ppp_channel.h b/include/linux/ppp_channel.h
index f73fbea0dbc2..ca8ad03eeef0 100644
--- a/include/linux/ppp_channel.h
+++ b/include/linux/ppp_channel.h
@@ -55,7 +55,7 @@ extern void ppp_input(struct ppp_channel *, struct sk_buff *);
 
 /* Called by the channel when an input error occurs, indicating
    that we may have missed a packet. */
-extern void ppp_input_error(struct ppp_channel *, int code);
+extern void ppp_input_error(struct ppp_channel *);
 
 /* Attach a channel to a given PPP unit in specified net. */
 extern int ppp_register_net_channel(struct net *, struct ppp_channel *);
diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c
index 2574aae3e066..e3c422dc533a 100644
--- a/net/atm/pppoatm.c
+++ b/net/atm/pppoatm.c
@@ -228,7 +228,7 @@ static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb)
 
 error:
 	kfree_skb(skb);
-	ppp_input_error(&pvcc->chan, 0);
+	ppp_input_error(&pvcc->chan);
 }
 
 static int pppoatm_may_send(struct pppoatm_vcc *pvcc, int size)
-- 
2.43.0

Re: [PATCH net-next] ppp: simplify input error handling

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri,  6 Mar 2026 17:36:49 +0800 you wrote:
> Currently, ppp_input_error() indicates an error by allocating a 0-length
> skb and calling ppp_do_recv(). It takes an error code argument, which is
> stored in skb->cb, but not used by ppp_receive_frame().
> 
> Simplify the error handling by removing the unused parameter and the
> unnecessary skb allocation. Instead, call ppp_receive_error() directly
> from ppp_input_error() under the recv lock, and the length check in
> ppp_receive_frame() can be removed.
> 
> [...]

Here is the summary with links:
  - [net-next] ppp: simplify input error handling
    https://git.kernel.org/netdev/net-next/c/abb0eb0b033a

You are awesome, thank you!
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