From b5cdae3291f7be7a34e75affe4c0ec1f7f328b64 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Tue, 18 Apr 2017 15:36:58 -0400 Subject: net: Generic XDP This provides a generic SKB based non-optimized XDP path which is used if either the driver lacks a specific XDP implementation, or the user requests it via a new IFLA_XDP_FLAGS value named XDP_FLAGS_SKB_MODE. It is arguable that perhaps I should have required something like this as part of the initial XDP feature merge. I believe this is critical for two reasons: 1) Accessibility. More people can play with XDP with less dependencies. Yes I know we have XDP support in virtio_net, but that just creates another depedency for learning how to use this facility. I wrote this to make life easier for the XDP newbies. 2) As a model for what the expected semantics are. If there is a pure generic core implementation, it serves as a semantic example for driver folks adding XDP support. One thing I have not tried to address here is the issue of XDP_PACKET_HEADROOM, thanks to Daniel for spotting that. It seems incredibly expensive to do a skb_cow(skb, XDP_PACKET_HEADROOM) or whatever even if the XDP program doesn't try to push headers at all. I think we really need the verifier to somehow propagate whether certain XDP helpers are used or not. v5: - Handle both negative and positive offset after running prog - Fix mac length in XDP_TX case (Alexei) - Use rcu_dereference_protected() in free_netdev (kbuild test robot) v4: - Fix MAC header adjustmnet before calling prog (David Ahern) - Disable LRO when generic XDP is installed (Michael Chan) - Bypass qdisc et al. on XDP_TX and record the event (Alexei) - Do not perform generic XDP on reinjected packets (DaveM) v3: - Make sure XDP program sees packet at MAC header, push back MAC header if we do XDP_TX. (Alexei) - Elide GRO when generic XDP is in use. (Alexei) - Add XDP_FLAG_SKB_MODE flag which the user can use to request generic XDP even if the driver has an XDP implementation. (Alexei) - Report whether SKB mode is in use in rtnl_xdp_fill() via XDP_FLAGS attribute. (Daniel) v2: - Add some "fall through" comments in switch statements based upon feedback from Andrew Lunn - Use RCU for generic xdp_prog, thanks to Johannes Berg. Tested-by: Andy Gospodarek Tested-by: Jesper Dangaard Brouer Tested-by: David Ahern Signed-off-by: David S. Miller --- net/core/rtnetlink.c | 40 +++++++++++++++++++++++++--------------- 1 file changed, 25 insertions(+), 15 deletions(-) (limited to 'net/core/rtnetlink.c') diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 088f9c8b4196..9031a6c8bfa7 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -896,15 +896,13 @@ static size_t rtnl_port_size(const struct net_device *dev, return port_self_size; } -static size_t rtnl_xdp_size(const struct net_device *dev) +static size_t rtnl_xdp_size(void) { size_t xdp_size = nla_total_size(0) + /* nest IFLA_XDP */ - nla_total_size(1); /* XDP_ATTACHED */ + nla_total_size(1) + /* XDP_ATTACHED */ + nla_total_size(4); /* XDP_FLAGS */ - if (!dev->netdev_ops->ndo_xdp) - return 0; - else - return xdp_size; + return xdp_size; } static noinline size_t if_nlmsg_size(const struct net_device *dev, @@ -943,7 +941,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev, + nla_total_size(MAX_PHYS_ITEM_ID_LEN) /* IFLA_PHYS_PORT_ID */ + nla_total_size(MAX_PHYS_ITEM_ID_LEN) /* IFLA_PHYS_SWITCH_ID */ + nla_total_size(IFNAMSIZ) /* IFLA_PHYS_PORT_NAME */ - + rtnl_xdp_size(dev) /* IFLA_XDP */ + + rtnl_xdp_size() /* IFLA_XDP */ + nla_total_size(1); /* IFLA_PROTO_DOWN */ } @@ -1251,23 +1249,35 @@ static int rtnl_fill_link_ifmap(struct sk_buff *skb, struct net_device *dev) static int rtnl_xdp_fill(struct sk_buff *skb, struct net_device *dev) { - struct netdev_xdp xdp_op = {}; struct nlattr *xdp; + u32 xdp_flags = 0; + u8 val = 0; int err; - if (!dev->netdev_ops->ndo_xdp) - return 0; xdp = nla_nest_start(skb, IFLA_XDP); if (!xdp) return -EMSGSIZE; - xdp_op.command = XDP_QUERY_PROG; - err = dev->netdev_ops->ndo_xdp(dev, &xdp_op); - if (err) - goto err_cancel; - err = nla_put_u8(skb, IFLA_XDP_ATTACHED, xdp_op.prog_attached); + if (rcu_access_pointer(dev->xdp_prog)) { + xdp_flags = XDP_FLAGS_SKB_MODE; + val = 1; + } else if (dev->netdev_ops->ndo_xdp) { + struct netdev_xdp xdp_op = {}; + + xdp_op.command = XDP_QUERY_PROG; + err = dev->netdev_ops->ndo_xdp(dev, &xdp_op); + if (err) + goto err_cancel; + val = xdp_op.prog_attached; + } + err = nla_put_u8(skb, IFLA_XDP_ATTACHED, val); if (err) goto err_cancel; + if (xdp_flags) { + err = nla_put_u32(skb, IFLA_XDP_FLAGS, xdp_flags); + if (err) + goto err_cancel; + } nla_nest_end(skb, xdp); return 0; -- cgit v1.2.3