On Fri, Jul 18, 2025 at 10:52:38AM +0200, Paolo Abeni wrote:
Tap devices support GSO over UDP tunnel offload. Probe for such
feature in a similar manner to other offloads.
GSO over UDP tunnel needs to be enabled in addition to a "plain"
offload (TSO or USO).
No need to check separately for the outer header checksum offload:
the kernel is going to support both of them or none.
Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
v2 -> v3:
- use bool type for tap_probe_has_tunnel()
- rebased on top of 2deec9ab7d ("virtio-net: Move
virtio_net_get_features() down")
- _array -> _ex
v1 -> v2:
- peer_has_tunnel return a bool
- move TUN_F definition in net/tun-linux.h
---
hw/net/virtio-net.c | 37 +++++++++++++++++++++++++++++++++++++
include/net/net.h | 3 +++
net/net.c | 9 +++++++++
net/tap-bsd.c | 5 +++++
net/tap-linux.c | 11 +++++++++++
net/tap-linux.h | 9 +++++++++
net/tap-solaris.c | 5 +++++
net/tap-stub.c | 5 +++++
net/tap.c | 11 +++++++++++
net/tap_int.h | 1 +
10 files changed, 96 insertions(+)
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 53413ec4d5..70c85f7f77 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -649,6 +649,15 @@ static int peer_has_uso(VirtIONet *n)
return qemu_has_uso(qemu_get_queue(n->nic)->peer);
}
+static bool peer_has_tunnel(VirtIONet *n)
+{
+ if (!peer_has_vnet_hdr(n)) {
+ return false;
+ }
+
+ return qemu_has_tunnel(qemu_get_queue(n->nic)->peer);
+}
+
static void virtio_net_set_mrg_rx_bufs(VirtIONet *n, int mergeable_rx_bufs,
int version_1, int hash_report)
{
@@ -3070,6 +3079,13 @@ static void virtio_net_get_features(VirtIODevice *vdev,
uint64_t *features,
virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_USO4);
virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_USO6);
+ virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO);
+ virtio_clear_feature_ex(features, VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO);
+ virtio_clear_feature_ex(features,
+ VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_CSUM);
+ virtio_clear_feature_ex(features,
+ VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO_CSUM);
+
virtio_clear_feature_ex(features, VIRTIO_NET_F_HASH_REPORT);
}
@@ -3083,6 +3099,15 @@ static void virtio_net_get_features(VirtIODevice *vdev,
uint64_t *features,
virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_USO6);
}
+ if (!peer_has_tunnel(n)) {
+ virtio_clear_feature_ex(features, VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO);
+ virtio_clear_feature_ex(features, VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO);
+ virtio_clear_feature_ex(features,
+ VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_CSUM);
+ virtio_clear_feature_ex(features,
+ VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO_CSUM);
+ }
+
if (!get_vhost_net(nc->peer)) {
if (!use_own_hash) {
virtio_clear_feature_ex(features, VIRTIO_NET_F_HASH_REPORT);
@@ -4137,6 +4162,10 @@ static const VMStateDescription vmstate_virtio_net = {
.dev_unplug_pending = dev_unplug_pending,
};
+#define DEFINE_PROP_FEATURE(_name, _state, _field, _bit, _defval) \
+ DEFINE_PROP_BIT64(_name, _state, _field[VIRTIO_DWORD(_bit)], \
+ (_bit) % 64, _defval)
+
static const Property virtio_net_properties[] = {
DEFINE_PROP_BIT64("csum", VirtIONet, host_features,
VIRTIO_NET_F_CSUM, true),
@@ -4245,6 +4274,14 @@ static const Property virtio_net_properties[] = {
rss_data.specified_hash_types,
VIRTIO_NET_HASH_REPORT_UDPv6_EX - 1,
ON_OFF_AUTO_AUTO),
+ DEFINE_PROP_FEATURE("host_tunnel", VirtIONet, host_features_ex,
+ VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO, true),
+ DEFINE_PROP_FEATURE("host_tunnel_csum", VirtIONet, host_features_ex,
+ VIRTIO_NET_F_HOST_UDP_TUNNEL_GSO_CSUM, true),
+ DEFINE_PROP_FEATURE("guest_tunnel", VirtIONet, host_features_ex,
+ VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO, true),
+ DEFINE_PROP_FEATURE("guest_tunnel_csum", VirtIONet, host_features_ex,
+ VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO_CSUM, true),
IIUC, to avoid issue with live-migration, we should disable all of them
in `hw_compat_10_0` in hw/core/machine.c (e.g. like `host_uso`,
`guest_uso*` in hw_compat_8_1).
Thanks,
Stefano
};
static void virtio_net_class_init(ObjectClass *klass, const void *data)
diff --git a/include/net/net.h b/include/net/net.h
index 48ba333d02..9a9084690d 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -65,6 +65,7 @@ typedef void (NetClientDestructor)(NetClientState *);
typedef RxFilterInfo *(QueryRxFilter)(NetClientState *);
typedef bool (HasUfo)(NetClientState *);
typedef bool (HasUso)(NetClientState *);
+typedef bool (HasTunnel)(NetClientState *);
typedef bool (HasVnetHdr)(NetClientState *);
typedef bool (HasVnetHdrLen)(NetClientState *, int);
typedef void (SetOffload)(NetClientState *, const NetOffloads *);
@@ -95,6 +96,7 @@ typedef struct NetClientInfo {
NetPoll *poll;
HasUfo *has_ufo;
HasUso *has_uso;
+ HasTunnel *has_tunnel;
HasVnetHdr *has_vnet_hdr;
HasVnetHdrLen *has_vnet_hdr_len;
SetOffload *set_offload;
@@ -197,6 +199,7 @@ void qemu_set_info_str(NetClientState *nc,
void qemu_format_nic_info_str(NetClientState *nc, uint8_t macaddr[6]);
bool qemu_has_ufo(NetClientState *nc);
bool qemu_has_uso(NetClientState *nc);
+bool qemu_has_tunnel(NetClientState *nc);
bool qemu_has_vnet_hdr(NetClientState *nc);
bool qemu_has_vnet_hdr_len(NetClientState *nc, int len);
void qemu_set_offload(NetClientState *nc, const NetOffloads *ol);
diff --git a/net/net.c b/net/net.c
index 63872b6855..9536184a0c 100644
--- a/net/net.c
+++ b/net/net.c
@@ -522,6 +522,15 @@ bool qemu_has_uso(NetClientState *nc)
return nc->info->has_uso(nc);
}
+bool qemu_has_tunnel(NetClientState *nc)
+{
+ if (!nc || !nc->info->has_tunnel) {
+ return false;
+ }
+
+ return nc->info->has_tunnel(nc);
+}
+
bool qemu_has_vnet_hdr(NetClientState *nc)
{
if (!nc || !nc->info->has_vnet_hdr) {
diff --git a/net/tap-bsd.c b/net/tap-bsd.c
index 86b6edee94..751d4c819c 100644
--- a/net/tap-bsd.c
+++ b/net/tap-bsd.c
@@ -217,6 +217,11 @@ int tap_probe_has_uso(int fd)
return 0;
}
+bool tap_probe_has_tunnel(int fd)
+{
+ return false;
+}
+
void tap_fd_set_vnet_hdr_len(int fd, int len)
{
}
diff --git a/net/tap-linux.c b/net/tap-linux.c
index a1c58f74f5..e2628be798 100644
--- a/net/tap-linux.c
+++ b/net/tap-linux.c
@@ -196,6 +196,17 @@ int tap_probe_has_uso(int fd)
return 1;
}
+bool tap_probe_has_tunnel(int fd)
+{
+ unsigned offload;
+
+ offload = TUN_F_CSUM | TUN_F_TSO4 | TUN_F_UDP_TUNNEL_GSO;
+ if (ioctl(fd, TUNSETOFFLOAD, offload) < 0) {
+ return false;
+ }
+ return true;
+}
+
void tap_fd_set_vnet_hdr_len(int fd, int len)
{
if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
diff --git a/net/tap-linux.h b/net/tap-linux.h
index 9a58cecb7f..8cd6b5874b 100644
--- a/net/tap-linux.h
+++ b/net/tap-linux.h
@@ -53,4 +53,13 @@
#define TUN_F_USO4 0x20 /* I can handle USO for IPv4 packets */
#define TUN_F_USO6 0x40 /* I can handle USO for IPv6 packets */
+/* I can handle TSO/USO for UDP tunneled packets */
+#define TUN_F_UDP_TUNNEL_GSO 0x080
+
+/*
+ * I can handle TSO/USO for UDP tunneled packets requiring csum offload for
+ * the outer header
+ */
+#define TUN_F_UDP_TUNNEL_GSO_CSUM 0x100
+
#endif /* QEMU_TAP_LINUX_H */
diff --git a/net/tap-solaris.c b/net/tap-solaris.c
index 833c066bee..ac1ae25761 100644
--- a/net/tap-solaris.c
+++ b/net/tap-solaris.c
@@ -222,6 +222,11 @@ int tap_probe_has_uso(int fd)
return 0;
}
+bool tap_probe_has_tunnel(int fd)
+{
+ return false;
+}
+
void tap_fd_set_vnet_hdr_len(int fd, int len)
{
}
diff --git a/net/tap-stub.c b/net/tap-stub.c
index 67d14ad4d5..f7a5e0c163 100644
--- a/net/tap-stub.c
+++ b/net/tap-stub.c
@@ -52,6 +52,11 @@ int tap_probe_has_uso(int fd)
return 0;
}
+bool tap_probe_has_tunnel(int fd)
+{
+ return false;
+}
+
void tap_fd_set_vnet_hdr_len(int fd, int len)
{
}
diff --git a/net/tap.c b/net/tap.c
index b49db19f83..23c6c118e7 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -76,6 +76,7 @@ typedef struct TAPState {
bool using_vnet_hdr;
bool has_ufo;
bool has_uso;
+ bool has_tunnel;
bool enabled;
VHostNetState *vhost_net;
unsigned host_vnet_hdr_len;
@@ -241,6 +242,14 @@ static bool tap_has_uso(NetClientState *nc)
return s->has_uso;
}
+static bool tap_has_tunnel(NetClientState *nc)
+{
+ TAPState *s = DO_UPCAST(TAPState, nc, nc);
+
+ assert(nc->info->type == NET_CLIENT_DRIVER_TAP);
+ return s->has_tunnel;
+}
+
static bool tap_has_vnet_hdr(NetClientState *nc)
{
TAPState *s = DO_UPCAST(TAPState, nc, nc);
@@ -369,6 +378,7 @@ static NetClientInfo net_tap_info = {
.cleanup = tap_cleanup,
.has_ufo = tap_has_ufo,
.has_uso = tap_has_uso,
+ .has_tunnel = tap_has_tunnel,
.has_vnet_hdr = tap_has_vnet_hdr,
.has_vnet_hdr_len = tap_has_vnet_hdr_len,
.set_offload = tap_set_offload,
@@ -398,6 +408,7 @@ static TAPState *net_tap_fd_init(NetClientState *peer,
s->using_vnet_hdr = false;
s->has_ufo = tap_probe_has_ufo(s->fd);
s->has_uso = tap_probe_has_uso(s->fd);
+ s->has_tunnel = tap_probe_has_tunnel(s->fd);
s->enabled = true;
tap_set_offload(&s->nc, &ol);
/*
diff --git a/net/tap_int.h b/net/tap_int.h
index f8bbe1cb0c..b76a05044b 100644
--- a/net/tap_int.h
+++ b/net/tap_int.h
@@ -38,6 +38,7 @@ void tap_set_sndbuf(int fd, const NetdevTapOptions *tap,
Error **errp);
int tap_probe_vnet_hdr(int fd, Error **errp);
int tap_probe_has_ufo(int fd);
int tap_probe_has_uso(int fd);
+bool tap_probe_has_tunnel(int fd);
void tap_fd_set_offload(int fd, const NetOffloads *ol);
void tap_fd_set_vnet_hdr_len(int fd, int len);
int tap_fd_set_vnet_le(int fd, int vnet_is_le);
--
2.50.0
