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Date: Fri, 24 Apr 2020 10:57:42 +0200
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org
Cc: davem@...emloft.net, kuba@...nel.org,
prashantbhole.linux@...il.com, jasowang@...hat.com,
brouer@...hat.com, toshiaki.makita1@...il.com,
daniel@...earbox.net, john.fastabend@...il.com, ast@...nel.org,
kafai@...com, songliubraving@...com, yhs@...com, andriin@...com,
dsahern@...il.com, David Ahern <dahern@...italocean.com>
Subject: Re: [PATCH v2 bpf-next 06/17] net: Add IFLA_XDP_EGRESS for XDP programs in the egress path
David Ahern <dsahern@...nel.org> writes:
> From: David Ahern <dahern@...italocean.com>
>
> Running programs in the egress path, on skbs or xdp_frames, does not
> require driver specific resources like Rx path. Accordingly, the
> programs can be run in core code, so add xdp_egress_prog to net_device
> to hold a reference to an attached program.
>
> For UAPI, add IFLA_XDP_EGRESS to if_link.h to specify egress programs,
> add a new attach flag, XDP_ATTACHED_EGRESS_CORE, to denote the
> attach point is at the core level (as opposed to driver or hardware)
> and add IFLA_XDP_EGRESS_CORE_PROG_ID for reporting the program id.
>
> Add egress argument to do_setlink_xdp to denote processing of
> IFLA_XDP_EGRESS versus IFLA_XDP, and add a check that none of the
> existing modes (SKB, DRV or HW) are set since those modes are not
> valid. The expectation is that XDP_FLAGS_HW_MODE will be used later
> (e.g., offloading guest programs).
>
> Add rtnl_xdp_egress_fill and helpers as the egress counterpart to the
> existing rtnl_xdp_fill.
>
> Signed-off-by: David Ahern <dahern@...italocean.com>
> ---
> include/linux/netdevice.h | 1 +
> include/uapi/linux/if_link.h | 3 +
> net/core/rtnetlink.c | 102 +++++++++++++++++++++++++++--
> tools/include/uapi/linux/if_link.h | 3 +
> 4 files changed, 105 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index a416c838b0ec..e157aed04e91 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1996,6 +1996,7 @@ struct net_device {
> unsigned int real_num_rx_queues;
>
> struct bpf_prog __rcu *xdp_prog;
> + struct bpf_prog __rcu *xdp_egress_prog;
> unsigned long gro_flush_timeout;
> rx_handler_func_t __rcu *rx_handler;
> void __rcu *rx_handler_data;
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 127c704eeba9..b3c6cb2f0f0a 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -170,6 +170,7 @@ enum {
> IFLA_PROP_LIST,
> IFLA_ALT_IFNAME, /* Alternative ifname */
> IFLA_PERM_ADDRESS,
> + IFLA_XDP_EGRESS, /* nested attribute with 1 or more IFLA_XDP_ attrs */
> __IFLA_MAX
> };
>
> @@ -988,6 +989,7 @@ enum {
> XDP_ATTACHED_SKB,
> XDP_ATTACHED_HW,
> XDP_ATTACHED_MULTI,
> + XDP_ATTACHED_EGRESS_CORE,
> };
>
> enum {
> @@ -1000,6 +1002,7 @@ enum {
> IFLA_XDP_SKB_PROG_ID,
> IFLA_XDP_HW_PROG_ID,
> IFLA_XDP_EXPECTED_FD,
> + IFLA_XDP_EGRESS_CORE_PROG_ID,
> __IFLA_XDP_MAX,
> };
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 4a3e85413688..e6f0eec99058 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -1037,7 +1037,7 @@ 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() /* IFLA_XDP */
> + + rtnl_xdp_size() * 2 /* IFLA_XDP and IFLA_XDP_EGRESS */
> + nla_total_size(4) /* IFLA_EVENT */
> + nla_total_size(4) /* IFLA_NEW_NETNSID */
> + nla_total_size(4) /* IFLA_NEW_IFINDEX */
> @@ -1402,6 +1402,42 @@ static int rtnl_fill_link_ifmap(struct sk_buff *skb, struct net_device *dev)
> return 0;
> }
>
> +static u32 rtnl_xdp_egress_prog(struct net_device *dev)
> +{
> + const struct bpf_prog *prog;
> +
> + ASSERT_RTNL();
> +
> + prog = rtnl_dereference(dev->xdp_egress_prog);
> + if (!prog)
> + return 0;
> + return prog->aux->id;
> +}
> +
> +static int rtnl_xdp_egress_report(struct sk_buff *skb, struct net_device *dev,
> + u32 *prog_id, u8 *mode, u8 tgt_mode, u32 attr,
> + u32 (*get_prog_id)(struct net_device *dev))
> +{
> + u32 curr_id;
> + int err;
> +
> + curr_id = get_prog_id(dev);
> + if (!curr_id)
> + return 0;
> +
> + *prog_id = curr_id;
> + err = nla_put_u32(skb, attr, curr_id);
> + if (err)
> + return err;
> +
> + if (*mode != XDP_ATTACHED_NONE)
> + *mode = XDP_ATTACHED_MULTI;
> + else
> + *mode = tgt_mode;
> +
> + return 0;
> +}
> +
> static u32 rtnl_xdp_prog_skb(struct net_device *dev)
> {
> const struct bpf_prog *generic_xdp_prog;
> @@ -1493,6 +1529,42 @@ static int rtnl_xdp_fill(struct sk_buff *skb, struct net_device *dev)
> return err;
> }
>
> +static int rtnl_xdp_egress_fill(struct sk_buff *skb, struct net_device *dev)
> +{
> + u8 mode = XDP_ATTACHED_NONE;
> + struct nlattr *xdp;
> + u32 prog_id = 0;
> + int err;
> +
> + xdp = nla_nest_start_noflag(skb, IFLA_XDP_EGRESS);
> + if (!xdp)
> + return -EMSGSIZE;
> +
> + err = rtnl_xdp_egress_report(skb, dev, &prog_id, &mode,
> + XDP_ATTACHED_EGRESS_CORE,
> + IFLA_XDP_EGRESS_CORE_PROG_ID,
> + rtnl_xdp_egress_prog);
> + if (err)
> + goto err_cancel;
> +
> + err = nla_put_u8(skb, IFLA_XDP_ATTACHED, mode);
> + if (err)
> + goto err_cancel;
> +
> + if (prog_id && mode != XDP_ATTACHED_MULTI) {
> + err = nla_put_u32(skb, IFLA_XDP_PROG_ID, prog_id);
> + if (err)
> + goto err_cancel;
> + }
> +
> + nla_nest_end(skb, xdp);
> + return 0;
> +
> +err_cancel:
> + nla_nest_cancel(skb, xdp);
> + return err;
> +}
> +
> static u32 rtnl_get_event(unsigned long event)
> {
> u32 rtnl_event_type = IFLA_EVENT_NONE;
> @@ -1750,6 +1822,9 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
> if (rtnl_xdp_fill(skb, dev))
> goto nla_put_failure;
>
> + if (rtnl_xdp_egress_fill(skb, dev))
> + goto nla_put_failure;
> +
> if (dev->rtnl_link_ops || rtnl_have_link_slave_info(dev)) {
> if (rtnl_link_fill(skb, dev) < 0)
> goto nla_put_failure;
> @@ -1834,6 +1909,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
> [IFLA_ALT_IFNAME] = { .type = NLA_STRING,
> .len = ALTIFNAMSIZ - 1 },
> [IFLA_PERM_ADDRESS] = { .type = NLA_REJECT },
> + [IFLA_XDP_EGRESS] = { .type = NLA_NESTED },
> };
>
> static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
> @@ -2489,7 +2565,8 @@ static int do_set_master(struct net_device *dev, int ifindex,
> #define DO_SETLINK_NOTIFY 0x03
>
> static int do_setlink_xdp(struct net_device *dev, struct nlattr *tb,
> - int *status, struct netlink_ext_ack *extack)
> + int *status, bool egress,
> + struct netlink_ext_ack *extack)
> {
> struct nlattr *xdp[IFLA_XDP_MAX + 1];
> u32 xdp_flags = 0;
> @@ -2505,6 +2582,10 @@ static int do_setlink_xdp(struct net_device *dev, struct nlattr *tb,
>
> if (xdp[IFLA_XDP_FLAGS]) {
> xdp_flags = nla_get_u32(xdp[IFLA_XDP_FLAGS]);
> + if (egress && xdp_flags & XDP_FLAGS_MODES) {
> + NL_SET_ERR_MSG(extack, "XDP_FLAGS_MODES not valid for egress");
> + goto out_einval;
> + }
> if (xdp_flags & ~XDP_FLAGS_MASK)
> goto out_einval;
> if (hweight32(xdp_flags & XDP_FLAGS_MODES) > 1)
> @@ -2522,7 +2603,7 @@ static int do_setlink_xdp(struct net_device *dev, struct nlattr *tb,
>
> err = dev_change_xdp_fd(dev, extack,
> nla_get_s32(xdp[IFLA_XDP_FD]),
> - expected_fd, xdp_flags, false);
> + expected_fd, xdp_flags, egress);
> if (err)
> return err;
>
> @@ -2827,8 +2908,21 @@ static int do_setlink(const struct sk_buff *skb,
> status |= DO_SETLINK_NOTIFY;
> }
>
> + if (tb[IFLA_XDP] && tb[IFLA_XDP_EGRESS]) {
> + NL_SET_ERR_MSG(extack, "IFLA_XDP and IFLA_XDP_EGRESS can not be configured at the same time");
> + err = -EINVAL;
> + goto errout;
> + }
> +
> if (tb[IFLA_XDP]) {
> - err = do_setlink_xdp(dev, tb[IFLA_XDP], &status, extack);
> + err = do_setlink_xdp(dev, tb[IFLA_XDP], &status, false, extack);
> + if (err)
> + goto errout;
> + }
> +
> + if (tb[IFLA_XDP_EGRESS]) {
> + err = do_setlink_xdp(dev, tb[IFLA_XDP_EGRESS], &status, true,
> + extack);
While testing this yesterday, I ran into an issue where attaching an
XDP_EGRESS program would return no error, but nothing was happening.
Spent quite a bit of time scratching my head until I realised that my
test machine had failed to boot the patched kernel, and had fallen back
to an earlier version; i.e., didn't have any xdp_egress support at all.
I think this will be a problem: Since we don't reject unknown netlink
attributes, userspace can't know if xdp_egress is supported. So maybe
it's better to just re-use IFLA_XDP with a new flag, instead of using a
separate attribute?
-Toke
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