[PATCH 2/2] tap: initialize TAPState->enabled according to the actual state of queue

[Andrey Ryabinin]

Currently TAPState->enabled initialized as true. If fd was passed to qemu
in a disabled state it will cause an assert at the attempt to detach queue
in virtio_net_set_queues():

virtio_net_set_queues() :
            r = peer_detach() -> tap_disable():
                                    if (s->enabled == 0) {
                                       return 0;
                                    } else {
                                       //Will return an error.
                                       ret = tap_fd_disable(s->fd);
                                       ...
                                       return ret;
            assert(!r);

Initialize ->enabled according to the actual state of fd to fix this.

Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
---
 net/tap-bsd.c     |  5 +++++
 net/tap-linux.c   | 12 ++++++++++++
 net/tap-solaris.c |  5 +++++
 net/tap.c         |  2 +-
 net/tap_int.h     |  1 +
 5 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/net/tap-bsd.c b/net/tap-bsd.c
index 005ce05c6e0..8c21f058c8c 100644
--- a/net/tap-bsd.c
+++ b/net/tap-bsd.c
@@ -217,6 +217,11 @@ int tap_probe_vnet_hdr_len(int fd, int len)
     return 0;
 }
 
+bool tap_probe_enabled(int fd)
+{
+    return true;
+}
+
 void tap_fd_set_vnet_hdr_len(int fd, int len)
 {
 }
diff --git a/net/tap-linux.c b/net/tap-linux.c
index 304ff45071d..6078ba03af6 100644
--- a/net/tap-linux.c
+++ b/net/tap-linux.c
@@ -193,6 +193,18 @@ int tap_probe_vnet_hdr_len(int fd, int len)
     return 1;
 }
 
+bool tap_probe_enabled(int fd)
+{
+    struct ifreq ifr;
+
+    if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
+        error_report("TUNGETIFF ioctl() failed: %s",
+                     strerror(errno));
+        return false;
+    }
+    return !(ifr.ifr_flags & IFF_DETACH_QUEUE);
+}
+
 void tap_fd_set_vnet_hdr_len(int fd, int len)
 {
     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
diff --git a/net/tap-solaris.c b/net/tap-solaris.c
index a44f8805c23..ccaa3334882 100644
--- a/net/tap-solaris.c
+++ b/net/tap-solaris.c
@@ -221,6 +221,11 @@ int tap_probe_vnet_hdr_len(int fd, int len)
     return 0;
 }
 
+bool tap_probe_enabled(int fd)
+{
+    return true;
+}
+
 void tap_fd_set_vnet_hdr_len(int fd, int len)
 {
 }
diff --git a/net/tap.c b/net/tap.c
index b3ddfd4a74b..799f8ec7c76 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -399,7 +399,7 @@ static TAPState *net_tap_fd_init(NetClientState *peer,
     s->host_vnet_hdr_len = vnet_hdr ? sizeof(struct virtio_net_hdr) : 0;
     s->using_vnet_hdr = false;
     s->has_ufo = tap_probe_has_ufo(s->fd);
-    s->enabled = true;
+    s->enabled = tap_probe_enabled(s->fd);
     tap_set_offload(&s->nc, 0, 0, 0, 0, 0);
     /*
      * Make sure host header length is set correctly in tap:
diff --git a/net/tap_int.h b/net/tap_int.h
index 547f8a5a28f..b8fc3dfbfa7 100644
--- a/net/tap_int.h
+++ b/net/tap_int.h
@@ -37,6 +37,7 @@ void tap_set_sndbuf(int fd, const NetdevTapOptions *tap, 
Error **errp);
 int tap_probe_vnet_hdr(int fd, Error **errp);
 int tap_probe_vnet_hdr_len(int fd, int len);
 int tap_probe_has_ufo(int fd);
+bool tap_probe_enabled(int fd);
 void tap_fd_set_offload(int fd, int csum, int tso4, int tso6, int ecn, int 
ufo);
 void tap_fd_set_vnet_hdr_len(int fd, int len);
 int tap_fd_set_vnet_le(int fd, int vnet_is_le);
-- 
2.35.1