From b5cdae3291f7be7a34e75affe4c0ec1f7f328b64 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Tue, 18 Apr 2017 15:36:58 -0400 Subject: [PATCH] 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 --- include/linux/netdevice.h | 8 ++ include/uapi/linux/if_link.h | 4 +- net/core/dev.c | 155 +++++++++++++++++++++++++++++++++-- net/core/gro_cells.c | 2 +- net/core/rtnetlink.c | 40 +++++---- 5 files changed, 187 insertions(+), 22 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 5d5267febd56..46d220c2bf92 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1905,9 +1905,17 @@ struct net_device { struct lock_class_key *qdisc_tx_busylock; struct lock_class_key *qdisc_running_key; bool proto_down; + struct bpf_prog __rcu *xdp_prog; }; #define to_net_dev(d) container_of(d, struct net_device, dev) +static inline bool netif_elide_gro(const struct net_device *dev) +{ + if (!(dev->features & NETIF_F_GRO) || dev->xdp_prog) + return true; + return false; +} + #define NETDEV_ALIGN 32 static inline diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h index 8b405afb2376..633aa0276d32 100644 --- a/include/uapi/linux/if_link.h +++ b/include/uapi/linux/if_link.h @@ -887,7 +887,9 @@ enum { /* XDP section */ #define XDP_FLAGS_UPDATE_IF_NOEXIST (1U << 0) -#define XDP_FLAGS_MASK (XDP_FLAGS_UPDATE_IF_NOEXIST) +#define XDP_FLAGS_SKB_MODE (2U << 0) +#define XDP_FLAGS_MASK (XDP_FLAGS_UPDATE_IF_NOEXIST | \ + XDP_FLAGS_SKB_MODE) enum { IFLA_XDP_UNSPEC, diff --git a/net/core/dev.c b/net/core/dev.c index db6e31564d06..1b3317c026c6 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -95,6 +95,7 @@ #include #include #include +#include #include #include #include @@ -4251,6 +4252,125 @@ static int __netif_receive_skb(struct sk_buff *skb) return ret; } +static struct static_key generic_xdp_needed __read_mostly; + +static int generic_xdp_install(struct net_device *dev, struct netdev_xdp *xdp) +{ + struct bpf_prog *new = xdp->prog; + int ret = 0; + + switch (xdp->command) { + case XDP_SETUP_PROG: { + struct bpf_prog *old = rtnl_dereference(dev->xdp_prog); + + rcu_assign_pointer(dev->xdp_prog, new); + if (old) + bpf_prog_put(old); + + if (old && !new) { + static_key_slow_dec(&generic_xdp_needed); + } else if (new && !old) { + static_key_slow_inc(&generic_xdp_needed); + dev_disable_lro(dev); + } + break; + } + + case XDP_QUERY_PROG: + xdp->prog_attached = !!rcu_access_pointer(dev->xdp_prog); + break; + + default: + ret = -EINVAL; + break; + } + + return ret; +} + +static u32 netif_receive_generic_xdp(struct sk_buff *skb, + struct bpf_prog *xdp_prog) +{ + struct xdp_buff xdp; + u32 act = XDP_DROP; + void *orig_data; + int hlen, off; + u32 mac_len; + + /* Reinjected packets coming from act_mirred or similar should + * not get XDP generic processing. + */ + if (skb_cloned(skb)) + return XDP_PASS; + + if (skb_linearize(skb)) + goto do_drop; + + /* The XDP program wants to see the packet starting at the MAC + * header. + */ + mac_len = skb->data - skb_mac_header(skb); + hlen = skb_headlen(skb) + mac_len; + xdp.data = skb->data - mac_len; + xdp.data_end = xdp.data + hlen; + xdp.data_hard_start = skb->data - skb_headroom(skb); + orig_data = xdp.data; + + act = bpf_prog_run_xdp(xdp_prog, &xdp); + + off = xdp.data - orig_data; + if (off > 0) + __skb_pull(skb, off); + else if (off < 0) + __skb_push(skb, -off); + + switch (act) { + case XDP_TX: + __skb_push(skb, mac_len); + /* fall through */ + case XDP_PASS: + break; + + default: + bpf_warn_invalid_xdp_action(act); + /* fall through */ + case XDP_ABORTED: + trace_xdp_exception(skb->dev, xdp_prog, act); + /* fall through */ + case XDP_DROP: + do_drop: + kfree_skb(skb); + break; + } + + return act; +} + +/* When doing generic XDP we have to bypass the qdisc layer and the + * network taps in order to match in-driver-XDP behavior. + */ +static void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog) +{ + struct net_device *dev = skb->dev; + struct netdev_queue *txq; + bool free_skb = true; + int cpu, rc; + + txq = netdev_pick_tx(dev, skb, NULL); + cpu = smp_processor_id(); + HARD_TX_LOCK(dev, txq, cpu); + if (!netif_xmit_stopped(txq)) { + rc = netdev_start_xmit(skb, dev, txq, 0); + if (dev_xmit_complete(rc)) + free_skb = false; + } + HARD_TX_UNLOCK(dev, txq); + if (free_skb) { + trace_xdp_exception(dev, xdp_prog, XDP_TX); + kfree_skb(skb); + } +} + static int netif_receive_skb_internal(struct sk_buff *skb) { int ret; @@ -4262,6 +4382,21 @@ static int netif_receive_skb_internal(struct sk_buff *skb) rcu_read_lock(); + if (static_key_false(&generic_xdp_needed)) { + struct bpf_prog *xdp_prog = rcu_dereference(skb->dev->xdp_prog); + + if (xdp_prog) { + u32 act = netif_receive_generic_xdp(skb, xdp_prog); + + if (act != XDP_PASS) { + rcu_read_unlock(); + if (act == XDP_TX) + generic_xdp_tx(skb, xdp_prog); + return NET_RX_DROP; + } + } + } + #ifdef CONFIG_RPS if (static_key_false(&rps_needed)) { struct rps_dev_flow voidflow, *rflow = &voidflow; @@ -4494,7 +4629,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff enum gro_result ret; int grow; - if (!(skb->dev->features & NETIF_F_GRO)) + if (netif_elide_gro(skb->dev)) goto normal; if (skb->csum_bad) @@ -6723,6 +6858,7 @@ EXPORT_SYMBOL(dev_change_proto_down); */ int dev_change_xdp_fd(struct net_device *dev, int fd, u32 flags) { + int (*xdp_op)(struct net_device *dev, struct netdev_xdp *xdp); const struct net_device_ops *ops = dev->netdev_ops; struct bpf_prog *prog = NULL; struct netdev_xdp xdp; @@ -6730,14 +6866,16 @@ int dev_change_xdp_fd(struct net_device *dev, int fd, u32 flags) ASSERT_RTNL(); - if (!ops->ndo_xdp) - return -EOPNOTSUPP; + xdp_op = ops->ndo_xdp; + if (!xdp_op || (flags & XDP_FLAGS_SKB_MODE)) + xdp_op = generic_xdp_install; + if (fd >= 0) { if (flags & XDP_FLAGS_UPDATE_IF_NOEXIST) { memset(&xdp, 0, sizeof(xdp)); xdp.command = XDP_QUERY_PROG; - err = ops->ndo_xdp(dev, &xdp); + err = xdp_op(dev, &xdp); if (err < 0) return err; if (xdp.prog_attached) @@ -6753,7 +6891,7 @@ int dev_change_xdp_fd(struct net_device *dev, int fd, u32 flags) xdp.command = XDP_SETUP_PROG; xdp.prog = prog; - err = ops->ndo_xdp(dev, &xdp); + err = xdp_op(dev, &xdp); if (err < 0 && prog) bpf_prog_put(prog); @@ -7793,6 +7931,7 @@ EXPORT_SYMBOL(alloc_netdev_mqs); void free_netdev(struct net_device *dev) { struct napi_struct *p, *n; + struct bpf_prog *prog; might_sleep(); netif_free_tx_queues(dev); @@ -7811,6 +7950,12 @@ void free_netdev(struct net_device *dev) free_percpu(dev->pcpu_refcnt); dev->pcpu_refcnt = NULL; + prog = rcu_dereference_protected(dev->xdp_prog, 1); + if (prog) { + bpf_prog_put(prog); + static_key_slow_dec(&generic_xdp_needed); + } + /* Compatibility with error handling in drivers */ if (dev->reg_state == NETREG_UNINITIALIZED) { netdev_freemem(dev); diff --git a/net/core/gro_cells.c b/net/core/gro_cells.c index c98bbfbd26b8..814e58a3ce8b 100644 --- a/net/core/gro_cells.c +++ b/net/core/gro_cells.c @@ -13,7 +13,7 @@ int gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb) struct net_device *dev = skb->dev; struct gro_cell *cell; - if (!gcells->cells || skb_cloned(skb) || !(dev->features & NETIF_F_GRO)) + if (!gcells->cells || skb_cloned(skb) || netif_elide_gro(dev)) return netif_rx(skb); cell = this_cpu_ptr(gcells->cells); 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; -- 2.20.1