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

[Brenden Blanco <bblanco@plumgrid.com>]

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 <bblanco@plumgrid.com>
---
 include/uapi/linux/if_link.h |  1 +
 net/core/rtnetlink.c         | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index c488066..08d66a3 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 f206677..1c4a603 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -909,6 +909,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
 	       + rtnl_link_get_af_size(dev, ext_filter_mask) /* IFLA_AF_SPEC */
 	       + 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(4) /* IFLA_BPF_FD */
 	       + nla_total_size(1); /* IFLA_PROTO_DOWN */
 
 }
@@ -1241,6 +1242,7 @@ 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)) ||
+	    nla_put_s32(skb, IFLA_BPF_FD, dev->bpf_valid) ||
 	    nla_put_u8(skb, IFLA_PROTO_DOWN, dev->proto_down))
 		goto nla_put_failure;
 
@@ -1374,6 +1376,7 @@ 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] = {
@@ -2028,6 +2031,13 @@ 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