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ppp: enable TX scatter-gather

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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: Qingfang Deng <dqfext@gmail.com>
Link: https://patch.msgid.link/20260129012902.941-1-dqfext@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Qingfang Deng 2026-01-29 09:29:02 +08:00 committed by Paolo Abeni
parent 3e5aa52b45
commit 42fcb213e5
1 changed files with 25 additions and 5 deletions
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30
drivers/net/ppp/ppp_generic.c
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@ -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;