[RFC PATCH v2 3/5] rtnl: add option for setting link bpf prog

[Brenden Blanco]

Sets the bpf program represented by fd as an early filter in the rx path
of the netdev. The fd must have been created as BPF_PROG_TYPE_PHYS_DEV.
Providing a negative value as fd clears the program. Getting the fd back
via rtnl is not possible, therefore reading of this value merely
provides a bool whether the program is valid on the link or not.

Signed-off-by: Brenden Blanco <bbla...@plumgrid.com>
---
 include/uapi/linux/if_link.h |  1 +
 net/core/rtnetlink.c         | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 9427f17..ccad234 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -155,6 +155,7 @@ enum {
        IFLA_PROTO_DOWN,
        IFLA_GSO_MAX_SEGS,
        IFLA_GSO_MAX_SIZE,
+       IFLA_BPF_FD,
        __IFLA_MAX
 };
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a75f7e9..96579ce 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -910,6 +910,7 @@ 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 */
+              + nla_total_size(4) /* IFLA_BPF_FD */
               + nla_total_size(1); /* IFLA_PROTO_DOWN */
 
 }
@@ -1242,6 +1243,9 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct 
net_device *dev,
             nla_put_string(skb, IFLA_IFALIAS, dev->ifalias)) ||
            nla_put_u32(skb, IFLA_CARRIER_CHANGES,
                        atomic_read(&dev->carrier_changes)) ||
+           (dev->netdev_ops->ndo_bpf_get &&
+            nla_put_s32(skb, IFLA_BPF_FD,
+                        dev->netdev_ops->ndo_bpf_get(dev))) ||
            nla_put_u8(skb, IFLA_PROTO_DOWN, dev->proto_down))
                goto nla_put_failure;
 
@@ -1375,6 +1379,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
        [IFLA_PHYS_SWITCH_ID]   = { .type = NLA_BINARY, .len = 
MAX_PHYS_ITEM_ID_LEN },
        [IFLA_LINK_NETNSID]     = { .type = NLA_S32 },
        [IFLA_PROTO_DOWN]       = { .type = NLA_U8 },
+       [IFLA_BPF_FD]           = { .type = NLA_S32 },
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
@@ -2029,6 +2034,13 @@ static int do_setlink(const struct sk_buff *skb,
                status |= DO_SETLINK_NOTIFY;
        }
 
+       if (tb[IFLA_BPF_FD]) {
+               err = dev_change_bpf_fd(dev, nla_get_s32(tb[IFLA_BPF_FD]));
+               if (err)
+                       goto errout;
+               status |= DO_SETLINK_NOTIFY;
+       }
+
 errout:
        if (status & DO_SETLINK_MODIFIED) {
                if (status & DO_SETLINK_NOTIFY)
-- 
2.8.0