net: netmap: implement virtio-net header probe

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 <[email protected]>

---
 net/netmap.c | 70 ++++++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 44 insertions(+), 26 deletions(-)

net/netmap.c +0 -0

index 9710321..f2dcaeb 100644

net/netmap.c +42 -24

 {
-    return true;
+    struct nmreq req;
+    int err;
+
+    /* 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);
+    if (err) {
+        if (err_report) {
+            error_report("Unable to execute NETMAP_BDG_VNET_HDR on %s: %s",
+                         s->ifname, strerror(errno));
+        }
+        return -1;
+    }
+
+    /* Keep track of the current length. */
+    s->vnet_hdr_len = len;
+
+    return 0;
 }
 
-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_do_set_vnet_hdr_len(s, len, false)) {
+        return false;
+    }
+
+    /* Restore the previous length. */
+    netmap_do_set_vnet_hdr_len(s, prev_len, true);
+
     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)

@@ -346,25 +381,8 @@ static void netmap_using_vnet_hdr(NetClientState *nc, bool enable)
 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);
-    if (err) {
-        error_report("Unable to execute NETMAP_BDG_VNET_HDR on %s: %s",
-                     s->ifname, strerror(errno));
-    } else {
-        /* Keep track of the current length. */
-        s->vnet_hdr_len = len;
-    }
+    netmap_do_set_vnet_hdr_len(s, len, true);
 }
 
 static void netmap_set_offload(NetClientState *nc, int csum, int tso4, int tso6,

@@ -376,7 +394,7 @@ static void netmap_set_offload(NetClientState *nc, int csum, int tso4, int tso6,
      * enables the offloadings.
      */
     if (!s->vnet_hdr_len) {
-        netmap_set_vnet_hdr_len(nc, sizeof(struct virtio_net_hdr));
+        netmap_do_set_vnet_hdr_len(s, sizeof(struct virtio_net_hdr), true);
     }
 }
 

net/netmap.c +0 -0

     .has_vnet_hdr = netmap_has_vnet_hdr,
     .has_vnet_hdr_len = netmap_has_vnet_hdr_len,
     .using_vnet_hdr = netmap_using_vnet_hdr,

Quoted 20 lines

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 <[email protected]>

---
 net/netmap.c | 70 ++++++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 44 insertions(+), 26 deletions(-)

net/netmap.c +0 -0

index 9710321..f2dcaeb 100644
@@ -323,20 +323,55 @@ static void netmap_cleanup(NetClientState *nc)
 }
 

net/netmap.c static void netmap_cleanup(NetClientState *nc) · line 326

Quoted 3 lines

net/netmap.c +1 -1

 /* Offloading manipulation support callbacks. */
-static bool netmap_has_ufo(NetClientState *nc)
+static int netmap_do_set_vnet_hdr_len(NetmapState *s, int len, bool err_report)

Passing something like err_report usually means it was the responsibility of caller to report. So let's remove the err_report and let caller to decide based on the return value.

Quoted 92 lines

net/netmap.c +42 -24

 {
-    return true;
+    struct nmreq req;
+    int err;
+
+    /* 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);
+    if (err) {
+        if (err_report) {
+            error_report("Unable to execute NETMAP_BDG_VNET_HDR on %s: %s",
+                         s->ifname, strerror(errno));
+        }
+        return -1;
+    }
+
+    /* Keep track of the current length. */
+    s->vnet_hdr_len = len;
+
+    return 0;
 }
 
-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_do_set_vnet_hdr_len(s, len, false)) {
+        return false;
+    }
+
+    /* Restore the previous length. */
+    netmap_do_set_vnet_hdr_len(s, prev_len, true);
+
     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)

@@ -346,25 +381,8 @@ static void netmap_using_vnet_hdr(NetClientState *nc, bool enable)
 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);
-    if (err) {
-        error_report("Unable to execute NETMAP_BDG_VNET_HDR on %s: %s",
-                     s->ifname, strerror(errno));
-    } else {
-        /* Keep track of the current length. */
-        s->vnet_hdr_len = len;
-    }
+    netmap_do_set_vnet_hdr_len(s, len, true);
 }
 
 static void netmap_set_offload(NetClientState *nc, int csum, int tso4, int tso6,

@@ -376,7 +394,7 @@ static void netmap_set_offload(NetClientState *nc, int csum, int tso4, int tso6,
      * enables the offloadings.
      */
     if (!s->vnet_hdr_len) {
-        netmap_set_vnet_hdr_len(nc, sizeof(struct virtio_net_hdr));
+        netmap_do_set_vnet_hdr_len(s, sizeof(struct virtio_net_hdr), true);
     }
 }
 

net/netmap.c static NetClientInfo net_netmap_info = { · line 409

Quoted 6 lines

net/netmap.c +1 -1

@@ -388,7 +406,7 @@ 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,

This look suspicious, I'm not sure this is correct for netmap. May need a comment to explain. Usually vnet hdr does not imply ufo.

Quoted 3 lines

net/netmap.c +0 -0

     .has_vnet_hdr = netmap_has_vnet_hdr,
     .has_vnet_hdr_len = netmap_has_vnet_hdr_len,
     .using_vnet_hdr = netmap_using_vnet_hdr,

Quoted 20 lines

Quoted 20 lines

static void netmap_set_offload(NetClientState *nc, int csum, int tso4, int tso6,

Quoted 9 lines

Quoted 9 lines

net/netmap.c +1 -1

@@ -376,7 +394,7 @@ static void netmap_set_offload(NetClientState *nc, int csum, int tso4, int tso6,
      * enables the offloadings.
      */
     if (!s->vnet_hdr_len) {
-        netmap_set_vnet_hdr_len(nc, sizeof(struct virtio_net_hdr));
+        netmap_do_set_vnet_hdr_len(s, sizeof(struct virtio_net_hdr), true);
     }
 }
 

Quoted 6 lines

net/netmap.c static NetClientInfo net_netmap_info = { · line 409

Quoted 6 lines

net/netmap.c +1 -1

@@ -388,7 +406,7 @@ 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,

This look suspicious, I'm not sure this is correct for netmap. May need a comment to explain. Usually vnet hdr does not imply ufo.

Quoted 4 lines

Quoted 4 lines

Quoted 3 lines

net/netmap.c static NetClientInfo net_netmap_info = { · line 412

Quoted 3 lines

net/netmap.c +0 -0

     .has_vnet_hdr = netmap_has_vnet_hdr,
     .has_vnet_hdr_len = netmap_has_vnet_hdr_len,
     .using_vnet_hdr = netmap_using_vnet_hdr,

Yes, I know it sounds weird in general, but a netmap port using virtio-net headers always provides TCPv4, TCPv6, UDP and ECN offloadings (done in software inside netmap).

This patch already provides a little comment about UFO support on the netmap_has_vnet_hdr() function.

Do you want me to move it here, or is
the comment not understandable enough?

Thanks for your review,
Vincenzo