[PATCH 1/3] bpf: Add support for mark with bpf_fib_lookup

[Rumen Telbizov <rumen.telbizov@menlosecurity.com>]

From: David Ahern <dsahern@kernel.org>

Add support for policy routing via marks to the bpf_fib_lookup
helper. The bpf_fib_lookup struct is constrained to 64B for
performance. Since the smac and dmac entries are used only for
output, put them in an anonymous struct and then add a union
around a second struct that contains the mark to use in the FIB
lookup.

Signed-off-by: Rumen Telbizov <rumen.telbizov@menlosecurity.com>
---
 include/uapi/linux/bpf.h | 16 ++++++++++++++--
 net/core/filter.c        |  4 ++--
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index ec6d85a81744..6c78cc9c3c75 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5925,8 +5925,20 @@ struct bpf_fib_lookup {
 	/* output */
 	__be16	h_vlan_proto;
 	__be16	h_vlan_TCI;
-	__u8	smac[6];     /* ETH_ALEN */
-	__u8	dmac[6];     /* ETH_ALEN */
+
+	union {
+		/* input */
+		struct {
+			__u32	mark;   /* fwmark for policy routing */
+			/* 2 4-byte holes for input */
+		};
+
+		/* output: source and dest mac */
+		struct {
+			__u8	smac[6];	/* ETH_ALEN */
+			__u8	dmac[6];	/* ETH_ALEN */
+		};
+	};
 };
 
 struct bpf_redir_neigh {
diff --git a/net/core/filter.c b/net/core/filter.c
index 65ab4e21c087..2ea997cacf4d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5299,6 +5299,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 	fl4.saddr = params->ipv4_src;
 	fl4.fl4_sport = params->sport;
 	fl4.fl4_dport = params->dport;
+	fl4.flowi4_mark = params->mark;
 	fl4.flowi4_multipath_hash = 0;
 
 	if (flags & BPF_FIB_LOOKUP_DIRECT) {
@@ -5311,7 +5312,6 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 
 		err = fib_table_lookup(tb, &fl4, &res, FIB_LOOKUP_NOREF);
 	} else {
-		fl4.flowi4_mark = 0;
 		fl4.flowi4_secid = 0;
 		fl4.flowi4_tun_key.tun_id = 0;
 		fl4.flowi4_uid = sock_net_uid(net, NULL);
@@ -5425,6 +5425,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 	fl6.saddr = *src;
 	fl6.fl6_sport = params->sport;
 	fl6.fl6_dport = params->dport;
+	fl6.flowi6_mark = params->mark;
 
 	if (flags & BPF_FIB_LOOKUP_DIRECT) {
 		u32 tbid = l3mdev_fib_table_rcu(dev) ? : RT_TABLE_MAIN;
@@ -5437,7 +5438,6 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		err = ipv6_stub->fib6_table_lookup(net, tb, oif, &fl6, &res,
 						   strict);
 	} else {
-		fl6.flowi6_mark = 0;
 		fl6.flowi6_secid = 0;
 		fl6.flowi6_tun_key.tun_id = 0;
 		fl6.flowi6_uid = sock_net_uid(net, NULL);
-- 
2.30.1 (Apple Git-130)