Messages in this thread | | | Date | Thu, 12 May 2022 18:54:46 +0200 | Subject | Re: [PATCH v2] can: skb: add extended skb support | From | Oliver Hartkopp <> |
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Hi Oleksij,
On 12.05.22 14:59, Oleksij Rempel wrote: > Add CAN specific skb extension support and add first currently needed > local_origin variable. > > On the CAN stack we push same skb data in different direction depending > on the interface type: > - to the HW egress and at same time back to the stack as echo > - over virtual vcan/vxcan interfaces as egress on one side and ingress on other > side of the vxcan tunnel. > We can't use skb->sk as marker of the origin, because not all packets > not all packets with local_origin are assigned to some socket. Some of > them are generate from the kernel, for example like J1939 control messages. > So, to properly detect flow direction is is better to store this information > as part of the SKB. > > The advantage of using skb_ext is that it is options and extendable > without affecting other skb users. It can be shared between cloned skbs and > duplicated only if needed. > > Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de> > Cc: Devid Antonio Filoni <devid.filoni@egluetechnologies.com> > --- > changes v2: > - migrate it to SKB_EXT
The use of SKB_EXT seems to be very costly to just store a boolean value.
What I could see from some of the other SKB_EXT users this extension (which performs alloc & COW) is used in special circumstances.
With your suggestion this additional effort is needed for every CAN related skb.
So at least for this use-case extending struct can_skb_priv seems to be more efficient.
https://elixir.bootlin.com/linux/latest/source/include/linux/can/skb.h#L44
We might get into problems with PF_PACKET sockets when extending the can_skb_priv length beyond HH_DATA_MOD, see:
https://elixir.bootlin.com/linux/latest/source/include/linux/can/skb.h#L99
But for now I'm not sure that SKB_EXT isn't too heavy to store that single flag.
Best regards, Oliver
> > drivers/net/can/vxcan.c | 4 ++++ > include/linux/can/skb.h | 4 ++++ > include/linux/skbuff.h | 3 +++ > net/can/Kconfig | 1 + > net/can/af_can.c | 5 +++++ > net/can/raw.c | 10 ++++++++-- > net/core/skbuff.c | 7 +++++++ > 7 files changed, 32 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/can/vxcan.c b/drivers/net/can/vxcan.c > index 577a80300514..93701a698008 100644 > --- a/drivers/net/can/vxcan.c > +++ b/drivers/net/can/vxcan.c > @@ -39,6 +39,7 @@ static netdev_tx_t vxcan_xmit(struct sk_buff *oskb, struct net_device *dev) > struct net_device *peer; > struct canfd_frame *cfd = (struct canfd_frame *)oskb->data; > struct net_device_stats *peerstats, *srcstats = &dev->stats; > + struct can_skb_ext *can_ext; > struct sk_buff *skb; > u8 len; > > @@ -66,6 +67,9 @@ static netdev_tx_t vxcan_xmit(struct sk_buff *oskb, struct net_device *dev) > skb->pkt_type = PACKET_BROADCAST; > skb->dev = peer; > skb->ip_summed = CHECKSUM_UNNECESSARY; > + can_ext = skb_ext_add(skb, SKB_EXT_CAN); > + if (can_ext) > + can_ext->local_origin = false; > > len = cfd->can_id & CAN_RTR_FLAG ? 0 : cfd->len; > if (netif_rx(skb) == NET_RX_SUCCESS) { > diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h > index fdb22b00674a..401b08890d74 100644 > --- a/include/linux/can/skb.h > +++ b/include/linux/can/skb.h > @@ -55,6 +55,10 @@ struct can_skb_priv { > struct can_frame cf[]; > }; > > +struct can_skb_ext { > + bool local_origin; > +}; > + > static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb) > { > return (struct can_skb_priv *)(skb->head); > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 3270cb72e4d8..d39e70e5f7f2 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -4563,6 +4563,9 @@ enum skb_ext_id { > #endif > #if IS_ENABLED(CONFIG_MCTP_FLOWS) > SKB_EXT_MCTP, > +#endif > +#if IS_ENABLED(CONFIG_CAN) > + SKB_EXT_CAN, > #endif > SKB_EXT_NUM, /* must be last */ > }; > diff --git a/net/can/Kconfig b/net/can/Kconfig > index a9ac5ffab286..eb826e3771fe 100644 > --- a/net/can/Kconfig > +++ b/net/can/Kconfig > @@ -5,6 +5,7 @@ > > menuconfig CAN > tristate "CAN bus subsystem support" > + select SKB_EXTENSIONS > help > Controller Area Network (CAN) is a slow (up to 1Mbit/s) serial > communications protocol. Development of the CAN bus started in > diff --git a/net/can/af_can.c b/net/can/af_can.c > index 1fb49d51b25d..329c540d3ddf 100644 > --- a/net/can/af_can.c > +++ b/net/can/af_can.c > @@ -201,6 +201,7 @@ int can_send(struct sk_buff *skb, int loop) > struct sk_buff *newskb = NULL; > struct canfd_frame *cfd = (struct canfd_frame *)skb->data; > struct can_pkg_stats *pkg_stats = dev_net(skb->dev)->can.pkg_stats; > + struct can_skb_ext *can_ext; > int err = -EINVAL; > > if (skb->len == CAN_MTU) { > @@ -240,6 +241,10 @@ int can_send(struct sk_buff *skb, int loop) > skb_reset_network_header(skb); > skb_reset_transport_header(skb); > > + can_ext = skb_ext_add(skb, SKB_EXT_CAN); > + if (can_ext) > + can_ext->local_origin = true; > + > if (loop) { > /* local loopback of sent CAN frames */ > > diff --git a/net/can/raw.c b/net/can/raw.c > index b7dbb57557f3..cba18cdf017f 100644 > --- a/net/can/raw.c > +++ b/net/can/raw.c > @@ -121,6 +121,7 @@ static void raw_rcv(struct sk_buff *oskb, void *data) > { > struct sock *sk = (struct sock *)data; > struct raw_sock *ro = raw_sk(sk); > + struct can_skb_ext *can_ext; > struct sockaddr_can *addr; > struct sk_buff *skb; > unsigned int *pflags; > @@ -173,8 +174,13 @@ static void raw_rcv(struct sk_buff *oskb, void *data) > /* add CAN specific message flags for raw_recvmsg() */ > pflags = raw_flags(skb); > *pflags = 0; > - if (oskb->sk) > - *pflags |= MSG_DONTROUTE; > + > + can_ext = skb_ext_find(oskb, SKB_EXT_CAN); > + if (can_ext) { > + if (can_ext->local_origin) > + *pflags |= MSG_DONTROUTE; > + } > + > if (oskb->sk == sk) > *pflags |= MSG_CONFIRM; > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 475183f37891..5a5409ccb767 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -61,6 +61,7 @@ > #include <linux/if_vlan.h> > #include <linux/mpls.h> > #include <linux/kcov.h> > +#include <linux/can/skb.h> > > #include <net/protocol.h> > #include <net/dst.h> > @@ -4338,6 +4339,9 @@ static const u8 skb_ext_type_len[] = { > #if IS_ENABLED(CONFIG_MCTP_FLOWS) > [SKB_EXT_MCTP] = SKB_EXT_CHUNKSIZEOF(struct mctp_flow), > #endif > +#if IS_ENABLED(CONFIG_CAN) > + [SKB_EXT_CAN] = SKB_EXT_CHUNKSIZEOF(struct can_skb_ext), > +#endif > }; > > static __always_inline unsigned int skb_ext_total_length(void) > @@ -4357,6 +4361,9 @@ static __always_inline unsigned int skb_ext_total_length(void) > #endif > #if IS_ENABLED(CONFIG_MCTP_FLOWS) > skb_ext_type_len[SKB_EXT_MCTP] + > +#endif > +#if IS_ENABLED(CONFIG_CAN) > + skb_ext_type_len[SKB_EXT_CAN] + > #endif > 0; > }
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