[PATCH net-next 2/2] cls_bpf: send back eBPF bytecode through netlink socket

[Quentin Monnet]

As for act_bpf in a former patch, this patch makes the scheduler send
eBPF bytecode through the netlink socket for BPF filters set up with tc.
The existing TCA_BPF_FLAGS netlink attribute is used to embed a new flag
signaling eBPF bytecode, so as to identify the BPF version when reading
from the socket on userspace side.

Signed-off-by: Quentin Monnet <quentin.mon...@6wind.com>
---
 include/uapi/linux/pkt_cls.h |  1 +
 net/sched/cls_bpf.c          | 25 +++++++++++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
index c43c5f78b9c4..09d726fc2c5a 100644
--- a/include/uapi/linux/pkt_cls.h
+++ b/include/uapi/linux/pkt_cls.h
@@ -376,6 +376,7 @@ enum {
 /* BPF classifier */
 
 #define TCA_BPF_FLAG_ACT_DIRECT                (1 << 0)
+#define TCA_BPF_FLAG_EBPF              (1 << 1)
 
 enum {
        TCA_BPF_UNSPEC,
diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
index 425fe6a0eda3..f1d9057d8d94 100644
--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -450,6 +450,25 @@ static int cls_bpf_dump_bpf_info(const struct cls_bpf_prog 
*prog,
 static int cls_bpf_dump_ebpf_info(const struct cls_bpf_prog *prog,
                                  struct sk_buff *skb)
 {
+       struct bpf_prog *filter;
+
+       rcu_read_lock();
+       filter = rcu_dereference(prog->filter);
+       if (filter) {
+               if (nla_put_u16(skb, TCA_BPF_OPS_LEN, filter->len)) {
+                       rcu_read_unlock();
+                       return -EMSGSIZE;
+               }
+
+               if (nla_put(skb, TCA_BPF_OPS,
+                           filter->len * sizeof(struct sock_filter),
+                           filter->insnsi)) {
+                       rcu_read_unlock();
+                       return -EMSGSIZE;
+               }
+       }
+       rcu_read_unlock();
+
        if (nla_put_u32(skb, TCA_BPF_FD, prog->bpf_fd))
                return -EMSGSIZE;
 
@@ -481,10 +500,12 @@ static int cls_bpf_dump(struct net *net, struct tcf_proto 
*tp, unsigned long fh,
            nla_put_u32(skb, TCA_BPF_CLASSID, prog->res.classid))
                goto nla_put_failure;
 
-       if (cls_bpf_is_ebpf(prog))
+       if (cls_bpf_is_ebpf(prog)) {
+               bpf_flags |= TCA_BPF_FLAG_EBPF;
                ret = cls_bpf_dump_ebpf_info(prog, skb);
-       else
+       } else {
                ret = cls_bpf_dump_bpf_info(prog, skb);
+       }
        if (ret)
                goto nla_put_failure;
 
-- 
2.7.4