net: sock: introduce SOCK_XDP

This patch introduces a new sock flag - SOCK_XDP. This will be used
for notifying the upper layer that XDP program is attached on the
lower socket, and requires for extra headroom.

TUN will be the first user.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 20 insertions, 0 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index ebd07ad82431..2c548bd20393 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -869,6 +869,9 @@ static int tun_attach(struct tun_struct *tun, struct file *file,
                 tun_napi_init(tun, tfile, napi);
         }
 
+        if (rtnl_dereference(tun->xdp_prog))
+                sock_set_flag(&tfile->sk, SOCK_XDP);
+
         tun_set_real_num_queues(tun);
 
         /* device is allowed to go away first, so no need to hold extra
@@ -1241,13 +1244,29 @@ static int tun_xdp_set(struct net_device *dev, struct bpf_prog *prog,
                        struct netlink_ext_ack *extack)
 {
         struct tun_struct *tun = netdev_priv(dev);
+        struct tun_file *tfile;
         struct bpf_prog *old_prog;
+        int i;
 
         old_prog = rtnl_dereference(tun->xdp_prog);
         rcu_assign_pointer(tun->xdp_prog, prog);
         if (old_prog)
                 bpf_prog_put(old_prog);
 
+        for (i = 0; i < tun->numqueues; i++) {
+                tfile = rtnl_dereference(tun->tfiles[i]);
+                if (prog)
+                        sock_set_flag(&tfile->sk, SOCK_XDP);
+                else
+                        sock_reset_flag(&tfile->sk, SOCK_XDP);
+        }
+        list_for_each_entry(tfile, &tun->disabled, next) {
+                if (prog)
+                        sock_set_flag(&tfile->sk, SOCK_XDP);
+                else
+                        sock_reset_flag(&tfile->sk, SOCK_XDP);
+        }
+
         return 0;
 }
 
diff --git a/include/net/sock.h b/include/net/sock.h
index 433f45fc2d68..38cae35f6e16 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -800,6 +800,7 @@ enum sock_flags {
         SOCK_SELECT_ERR_QUEUE, /* Wake select on error queue */
         SOCK_RCU_FREE, /* wait rcu grace period in sk_destruct() */
         SOCK_TXTIME,
+        SOCK_XDP, /* XDP is attached */
 };
 
 #define SK_FLAGS_TIMESTAMP ((1UL << SOCK_TIMESTAMP) | (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE))