[Qemu-devel] [PATCH v3] net: netmap: implement virtio-net header probe

[Qemu-devel] [PATCH v3] net: netmap: implement virtio-net header probe

[Vincenzo Maffione]

Current implementation for netmap backend does not really probe the netmap
kernel module to know whether virtio-net header is supported for a specific
netmap port. This is only correct for VALE ports, but it is not correct for
hardware ports, pipes, etc.

This patch properly implements the missing probe mechanism, fixing the
implementation of the involved hooks (has_vnet_hdr, has_vnet_hdr_len, has_ufo,
...).

CHANGELOG:
  - renamed netmap_do_set_vnet_hdr_len to netmap_fd_set_vnet_hdr_len
  - abort() when failing to restore previous vnet-hdr length
  - moved update to s->vnet_hdr_len to netmap_set_vnet_hdr_len

Vincenzo Maffione (1):
  net: netmap: probe netmap interface for virtio-net header

 net/netmap.c | 59 ++++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 38 insertions(+), 21 deletions(-)

-- 
2.7.1

[Qemu-devel] [PATCH v3] net: netmap: probe netmap interface for virtio-net header

[Vincenzo Maffione]

Previous implementation of has_ufo, has_vnet_hdr, has_vnet_hdr_len, etc.
did not really probe for virtio-net header support for the netmap
interface attached to the backend. These callbacks were correct for
VALE ports, but incorrect for hardware NICs, pipes, monitors, etc.

This patch fixes the implementation to work properly with all kinds
of netmap ports.

Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
---
 net/netmap.c | 59 ++++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 38 insertions(+), 21 deletions(-)

diff --git a/net/netmap.c b/net/netmap.c
index 9710321..1b42728 100644
--- a/net/netmap.c
+++ b/net/netmap.c
@@ -323,20 +323,47 @@ static void netmap_cleanup(NetClientState *nc)
 }
 
 /* Offloading manipulation support callbacks. */
-static bool netmap_has_ufo(NetClientState *nc)
+static int netmap_fd_set_vnet_hdr_len(NetmapState *s, int len)
 {
-    return true;
+    struct nmreq req;
+
+    /* Issue a NETMAP_BDG_VNET_HDR command to change the virtio-net header
+     * length for the netmap adapter associated to 's->ifname'.
+     */
+    memset(&req, 0, sizeof(req));
+    pstrcpy(req.nr_name, sizeof(req.nr_name), s->ifname);
+    req.nr_version = NETMAP_API;
+    req.nr_cmd = NETMAP_BDG_VNET_HDR;
+    req.nr_arg1 = len;
+
+    return ioctl(s->nmd->fd, NIOCREGIF, &req);
 }
 
-static bool netmap_has_vnet_hdr(NetClientState *nc)
+static bool netmap_has_vnet_hdr_len(NetClientState *nc, int len)
 {
+    NetmapState *s = DO_UPCAST(NetmapState, nc, nc);
+    int prev_len = s->vnet_hdr_len;
+
+    /* Check that we can set the new length. */
+    if (netmap_fd_set_vnet_hdr_len(s, len)) {
+        return false;
+    }
+
+    /* Restore the previous length. */
+    if (netmap_fd_set_vnet_hdr_len(s, prev_len)) {
+        error_report("Failed to restore vnet-hdr length %d on %s: %s",
+                     prev_len, s->ifname, strerror(errno));
+        abort();
+    }
+
     return true;
 }
 
-static bool netmap_has_vnet_hdr_len(NetClientState *nc, int len)
+/* A netmap interface that supports virtio-net headers always
+ * supports UFO, so we use this callback also for the has_ufo hook. */
+static bool netmap_has_vnet_hdr(NetClientState *nc)
 {
-    return len == 0 || len == sizeof(struct virtio_net_hdr) ||
-                len == sizeof(struct virtio_net_hdr_mrg_rxbuf);
+    return netmap_has_vnet_hdr_len(nc, sizeof(struct virtio_net_hdr));
 }
 
 static void netmap_using_vnet_hdr(NetClientState *nc, bool enable)
@@ -347,20 +374,11 @@ static void netmap_set_vnet_hdr_len(NetClientState *nc, int len)
 {
     NetmapState *s = DO_UPCAST(NetmapState, nc, nc);
     int err;
-    struct nmreq req;
 
-    /* Issue a NETMAP_BDG_VNET_HDR command to change the virtio-net header
-     * length for the netmap adapter associated to 's->ifname'.
-     */
-    memset(&req, 0, sizeof(req));
-    pstrcpy(req.nr_name, sizeof(req.nr_name), s->ifname);
-    req.nr_version = NETMAP_API;
-    req.nr_cmd = NETMAP_BDG_VNET_HDR;
-    req.nr_arg1 = len;
-    err = ioctl(s->nmd->fd, NIOCREGIF, &req);
+    err = netmap_fd_set_vnet_hdr_len(s, len);
     if (err) {
-        error_report("Unable to execute NETMAP_BDG_VNET_HDR on %s: %s",
-                     s->ifname, strerror(errno));
+        error_report("Unable to set vnet-hdr length %d on %s: %s",
+                     len, s->ifname, strerror(errno));
     } else {
         /* Keep track of the current length. */
         s->vnet_hdr_len = len;
@@ -373,8 +391,7 @@ static void netmap_set_offload(NetClientState *nc, int csum, int tso4, int tso6,
     NetmapState *s = DO_UPCAST(NetmapState, nc, nc);
 
     /* Setting a virtio-net header length greater than zero automatically
-     * enables the offloadings.
-     */
+     * enables the offloadings. */
     if (!s->vnet_hdr_len) {
         netmap_set_vnet_hdr_len(nc, sizeof(struct virtio_net_hdr));
     }
@@ -388,7 +405,7 @@ static NetClientInfo net_netmap_info = {
     .receive_iov = netmap_receive_iov,
     .poll = netmap_poll,
     .cleanup = netmap_cleanup,
-    .has_ufo = netmap_has_ufo,
+    .has_ufo = netmap_has_vnet_hdr,
     .has_vnet_hdr = netmap_has_vnet_hdr,
     .has_vnet_hdr_len = netmap_has_vnet_hdr_len,
     .using_vnet_hdr = netmap_using_vnet_hdr,
-- 
2.7.1

Re: [Qemu-devel] [PATCH v3] net: netmap: probe netmap interface for virtio-net header

[Jason Wang]

On 02/24/2016 06:30 PM, Vincenzo Maffione wrote:
> Previous implementation of has_ufo, has_vnet_hdr, has_vnet_hdr_len, etc.
> did not really probe for virtio-net header support for the netmap
> interface attached to the backend. These callbacks were correct for
> VALE ports, but incorrect for hardware NICs, pipes, monitors, etc.
>
> This patch fixes the implementation to work properly with all kinds
> of netmap ports.
>
> Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
> ---
>  net/netmap.c | 59 ++++++++++++++++++++++++++++++++++++++---------------------
>  1 file changed, 38 insertions(+), 21 deletions(-)
>

Applied to -net.

Thanks