Commit 42fcb213 authored by Qingfang Deng's avatar Qingfang Deng Committed by Paolo Abeni
Browse files

ppp: enable TX scatter-gather 



PPP channels using chan->direct_xmit prepend the PPP header to a skb and
call dev_queue_xmit() directly. In this mode the skb does not need to be
linear, but the PPP netdevice currently does not advertise
scatter-gather features, causing unnecessary linearization and
preventing GSO.

Enable NETIF_F_SG and NETIF_F_FRAGLIST on PPP devices. In case a linear
buffer is required (PPP compression, multilink, and channels without
direct_xmit), call skb_linearize() explicitly.

Signed-off-by: default avatarQingfang Deng <dqfext@gmail.com>
Link: https://patch.msgid.link/20260129012902.941-1-dqfext@gmail.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 3e5aa52b

drivers/net/ppp/ppp_generic.c

+25 −5
Original line number Diff line number Diff line
@@ -1641,6 +1641,8 @@ static void ppp_setup(struct net_device *dev) 
	dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;

	dev->priv_destructor = ppp_dev_priv_destructor;

	dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;

	dev->features = NETIF_F_SG | NETIF_F_FRAGLIST;

	dev->hw_features = dev->features;

	netif_keep_dst(dev);

}
@@ -1710,6 +1712,10 @@ pad_compress_skb(struct ppp *ppp, struct sk_buff *skb) 
		ppp->xcomp->comp_extra + ppp->dev->hard_header_len;

	int compressor_skb_size = ppp->dev->mtu +

		ppp->xcomp->comp_extra + PPP_HDRLEN;



	if (skb_linearize(skb))

		return NULL;



	new_skb = alloc_skb(new_skb_size, GFP_ATOMIC);

	if (!new_skb) {

		if (net_ratelimit())
@@ -1797,6 +1803,10 @@ ppp_send_frame(struct ppp *ppp, struct sk_buff *skb) 
	case PPP_IP:

		if (!ppp->vj || (ppp->flags & SC_COMP_TCP) == 0)

			break;



		if (skb_linearize(skb))

			goto drop;



		/* try to do VJ TCP header compression */

		new_skb = alloc_skb(skb->len + ppp->dev->hard_header_len - 2,

				    GFP_ATOMIC);
@@ -1894,19 +1904,26 @@ ppp_push(struct ppp *ppp) 
	}



	if ((ppp->flags & SC_MULTILINK) == 0) {

		struct ppp_channel *chan;

		/* not doing multilink: send it down the first channel */

		list = list->next;

		pch = list_entry(list, struct channel, clist);



		spin_lock(&pch->downl);

		if (pch->chan) {

			if (pch->chan->ops->start_xmit(pch->chan, skb))

				ppp->xmit_pending = NULL;

		} else {

			/* channel got unregistered */

		chan = pch->chan;

		if (unlikely(!chan || (!chan->direct_xmit && skb_linearize(skb)))) {

			/* channel got unregistered, or it requires a linear

			 * skb but linearization failed

			 */

			kfree_skb(skb);

			ppp->xmit_pending = NULL;

			goto out;

		}



		if (chan->ops->start_xmit(chan, skb))

			ppp->xmit_pending = NULL;



out:

		spin_unlock(&pch->downl);

		return;

	}
@@ -1991,6 +2008,8 @@ static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb) 
		return 0; /* can't take now, leave it in xmit_pending */



	/* Do protocol field compression */

	if (skb_linearize(skb))

		goto err_linearize;

	p = skb->data;

	len = skb->len;

	if (*p == 0 && mp_protocol_compress) {
@@ -2149,6 +2168,7 @@ static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb) 


 noskb:

	spin_unlock(&pch->downl);

 err_linearize:

	if (ppp->debug & 1)

		netdev_err(ppp->dev, "PPP: no memory (fragment)\n");

	++ppp->dev->stats.tx_errors;