[PATCH 2/3] net/tap: expose tap_get_mtu() via NetClientState

Add a public tap_get_mtu() function, following the same pattern
as the existing tap_get_fd(), to allow other subsystems (such as
virtio-net) to query a tap netdev's host MTU via its
NetClientState without depending on tap-internal headers.

This is a preparatory patch; the function is not yet called from
anywhere.

Signed-off-by: Nariman Sayed <[email protected]>
---
 include/net/tap.h | 1 +
 net/tap.c         | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/include/net/tap.h b/include/net/tap.h
index 6f34f13eae..6b478acbfb 100644
--- a/include/net/tap.h
+++ b/include/net/tap.h
@@ -32,5 +32,6 @@ int tap_enable(NetClientState *nc);
 int tap_disable(NetClientState *nc);
 
 int tap_get_fd(NetClientState *nc);
+int tap_get_mtu(NetClientState *nc);
 
 #endif /* QEMU_NET_TAP_H */
diff --git a/net/tap.c b/net/tap.c
index 57ffb09885..122319d5f3 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -379,6 +379,13 @@ int tap_get_fd(NetClientState *nc)
     return s->fd;
 }
 
+int tap_get_mtu(NetClientState *nc)
+{
+    TAPState *s = DO_UPCAST(TAPState, nc, nc);
+    assert(nc->info->type == NET_CLIENT_DRIVER_TAP);
+    return tap_fd_get_mtu(s->fd);
+}
+
 /*
  * tap_get_vhost_net() can return NULL if a tap net-device backend is
  * created with 'vhost=off' option, 'vhostforce=off' or no vhost or
-- 
2.34.1