> Lorenzo Bianconi <lorenzo@xxxxxxxxxx> writes:
>
> > Allow increasing the MTU over page boundaries on veth devices
> > if the attached xdp program declares to support xdp fragments.
> > Enable NETIF_F_ALL_TSO when the device is running in xdp mode.
> >
> > Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
> > ---
> > drivers/net/veth.c | 28 +++++++++++++++++-----------
> > 1 file changed, 17 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> > index 47b21b1d2fd9..c5a2dc2b2e4b 100644
> > --- a/drivers/net/veth.c
> > +++ b/drivers/net/veth.c
> > @@ -293,8 +293,7 @@ static int veth_forward_skb(struct net_device *dev, struct sk_buff *skb,
> > /* return true if the specified skb has chances of GRO aggregation
> > * Don't strive for accuracy, but try to avoid GRO overhead in the most
> > * common scenarios.
> > - * When XDP is enabled, all traffic is considered eligible, as the xmit
> > - * device has TSO off.
> > + * When XDP is enabled, all traffic is considered eligible.
> > * When TSO is enabled on the xmit device, we are likely interested only
> > * in UDP aggregation, explicitly check for that if the skb is suspected
> > * - the sock_wfree destructor is used by UDP, ICMP and XDP sockets -
> > @@ -302,11 +301,13 @@ static int veth_forward_skb(struct net_device *dev, struct sk_buff *skb,
> > */
> > static bool veth_skb_is_eligible_for_gro(const struct net_device *dev,
> > const struct net_device *rcv,
> > + const struct veth_rq *rq,
> > const struct sk_buff *skb)
> > {
> > - return !(dev->features & NETIF_F_ALL_TSO) ||
> > - (skb->destructor == sock_wfree &&
> > - rcv->features & (NETIF_F_GRO_FRAGLIST | NETIF_F_GRO_UDP_FWD));
> > + return rcu_access_pointer(rq->xdp_prog) ||
> > + !(dev->features & NETIF_F_ALL_TSO) ||
> > + (skb->destructor == sock_wfree &&
> > + rcv->features & (NETIF_F_GRO_FRAGLIST | NETIF_F_GRO_UDP_FWD));
> > }
> >
> > static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
> > @@ -335,7 +336,7 @@ static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
> > * Don't bother with napi/GRO if the skb can't be aggregated
> > */
> > use_napi = rcu_access_pointer(rq->napi) &&
> > - veth_skb_is_eligible_for_gro(dev, rcv, skb);
> > + veth_skb_is_eligible_for_gro(dev, rcv, rq, skb);
> > }
> >
> > skb_tx_timestamp(skb);
> > @@ -1525,9 +1526,14 @@ static int veth_xdp_set(struct net_device *dev, struct bpf_prog *prog,
> > goto err;
> > }
> >
> > - max_mtu = PAGE_SIZE - VETH_XDP_HEADROOM -
> > - peer->hard_header_len -
> > - SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> > + max_mtu = SKB_WITH_OVERHEAD(PAGE_SIZE - VETH_XDP_HEADROOM) -
> > + peer->hard_header_len;
>
> Why are we no longer accounting the size of the skb_shared_info if the
> program doesn't support frags?
doing so we do not allow packets over page boundaries (so non-linear xdp_buff)
if the attached program does not delclare to support them, right?
>
> > + /* Allow increasing the max_mtu if the program supports
> > + * XDP fragments.
> > + */
> > + if (prog->aux->xdp_has_frags)
> > + max_mtu += PAGE_SIZE * MAX_SKB_FRAGS;
> > +
> > if (peer->mtu > max_mtu) {
> > NL_SET_ERR_MSG_MOD(extack, "Peer MTU is too large to set XDP");
> > err = -ERANGE;
> > @@ -1549,7 +1555,7 @@ static int veth_xdp_set(struct net_device *dev, struct bpf_prog *prog,
> > }
> >
> > if (!old_prog) {
> > - peer->hw_features &= ~NETIF_F_GSO_SOFTWARE;
> > + peer->hw_features &= ~NETIF_F_GSO_FRAGLIST;
>
> The patch description says we're enabling TSO, but this change enables a
> couple of other flags as well. Also, it's not quite obvious to me why
> your change makes this possible? Is it because we can now execute XDP on
> a full TSO packet at once? Because then this should be coupled to the
> xdp_has_frags flag of the XDP program? Or will the TSO packet be
> segmented before it hits the XDP program? But then this change has
> nothing to do with the rest of your series?
actually tso support is not mandatory for this feature (even if it is probably
meaningful). I will drop it from v5 and we can take care of it in a susequent
patch.
Regards,
Lorenzo
>
> Please also add this explanation to the commit message :)
>
> -Toke
>
Attachment:
signature.asc
Description: PGP signature
