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Date: Fri, 15 Oct 2010 18:15:51 +0200 From: Oliver Hartkopp <socketcan@...tkopp.net> To: Kurt Van Dijck <kurt.van.dijck@....be> CC: netdev <netdev@...r.kernel.org>, socketcan-core@...ts.berlios.de Subject: Re: [PATCH V2 net-next] can-raw: add msg_flags to distinguish local traffic Hello Kurt, thanks for the patch. I really appreciate this extension. Some remarks inline ... On 15.10.2010 17:38, Kurt Van Dijck wrote: > diff --git a/Documentation/networking/can.txt b/Documentation/networking/can.txt > index cd79735..95341aa 100644 > --- a/Documentation/networking/can.txt > +++ b/Documentation/networking/can.txt > @@ -22,6 +22,7 @@ This file contains > 4.1.2 RAW socket option CAN_RAW_ERR_FILTER > 4.1.3 RAW socket option CAN_RAW_LOOPBACK > 4.1.4 RAW socket option CAN_RAW_RECV_OWN_MSGS > + 4.1.5 RAW socket returned flags > 4.2 Broadcast Manager protocol sockets (SOCK_DGRAM) > 4.3 connected transport protocols (SOCK_SEQPACKET) > 4.4 unconnected transport protocols (SOCK_DGRAM) > @@ -471,6 +472,16 @@ solution for a couple of reasons: > setsockopt(s, SOL_CAN_RAW, CAN_RAW_RECV_OWN_MSGS, > &recv_own_msgs, sizeof(recv_own_msgs)); > > + 4.1.5 RAW socket returned flags > + > + When using recvmsg() call, the msg->msg_flags may contain following flags: > + > + MSG_DONTROUTE: set when the frame was sent via the same physical device, > + ie. a loopback frame. According the code MSG_DONTROUTE indicates frames that have been originated on the local host. Nothing more. Only when you enabled CAN_RAW_RECV_OWN_MSGS and you bound the socket to a specific CAN interface, the description becomes correct. Better write: MSG_DONTROUTE : set when the received frame was created on the local host. > + MSG_CONFIRM: set when the frame was sent via the socket it is received on. ok. > + This flag acts as a 'transmission confirmation'. Better: This flag can be interpreted as a 'transmission confirmation' when the CAN driver supports the echo of CAN frames on driver level, see 3.2 and 6.2 > + In order to receive such messages, CAN_RAW_RECV_OWN_MSGS must be set. > + > 4.2 Broadcast Manager protocol sockets (SOCK_DGRAM) > 4.3 connected transport protocols (SOCK_SEQPACKET) > 4.4 unconnected transport protocols (SOCK_DGRAM) > diff --git a/net/can/raw.c b/net/can/raw.c > index 7d77e67..9020c4f 100644 > --- a/net/can/raw.c > +++ b/net/can/raw.c > @@ -90,23 +90,39 @@ struct raw_sock { > can_err_mask_t err_mask; > }; > > +/* > + * return some space to store extra msg flags in. > + * We use 1 int beyond the 'struct sockaddr_can' in skb->cb > + * to store those. > + * These flags will be use in raw_recvmsg() > + */ /* * Return pointer to store the extra msg flags for raw_recvmsg(). * We use the space of one unsigned int beyond the 'struct sockaddr_can' * in skb->cb. */ > +static inline unsigned int *raw_flags(struct sk_buff *skb) > +{ > + BUILD_BUG_ON(sizeof(skb->cb) <= (sizeof(struct sockaddr_can) > + + sizeof(unsigned int))); One empty line would be nice here ... > + /* return pointer after struct sockaddr_can */ > + return (unsigned int *)(&((struct sockaddr_can *)skb->cb)[1]); > +} > + > static inline struct raw_sock *raw_sk(const struct sock *sk) > { > return (struct raw_sock *)sk; > } > > -static void raw_rcv(struct sk_buff *skb, void *data) > +static void raw_rcv(struct sk_buff *oskb, void *data) > { > struct sock *sk = (struct sock *)data; > struct raw_sock *ro = raw_sk(sk); > struct sockaddr_can *addr; > + struct sk_buff *skb; > + unsigned int *pflags; > > /* check the received tx sock reference */ > - if (!ro->recv_own_msgs && skb->sk == sk) > + if (!ro->recv_own_msgs && oskb->sk == sk) > return; > > /* clone the given skb to be able to enqueue it into the rcv queue */ > - skb = skb_clone(skb, GFP_ATOMIC); > + skb = skb_clone(oskb, GFP_ATOMIC); > if (!skb) > return; > > @@ -123,6 +139,14 @@ static void raw_rcv(struct sk_buff *skb, void *data) > addr->can_family = AF_CAN; > addr->can_ifindex = skb->dev->ifindex; > > + /* prepare the flags for raw_recvmsg() */ > + pflags = raw_flags(skb); > + *pflags = 0; > + if (oskb->sk) > + *pflags |= MSG_DONTROUTE; > + if (oskb->sk == sk) > + *pflags |= MSG_CONFIRM; > + A good improvement since your first proof-of-concept code :-) > if (sock_queue_rcv_skb(sk, skb) < 0) > kfree_skb(skb); > } > @@ -707,6 +731,9 @@ static int raw_recvmsg(struct kiocb *iocb, struct socket *sock, > memcpy(msg->msg_name, skb->cb, msg->msg_namelen); > } > > + /* assign the flags that have been recorded in raw_rcv() */ > + msg->msg_flags |= *(raw_flags(skb)); > + dito :-) > skb_free_datagram(sk, skb); > > return size; Tnx & regards, Oliver -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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