net/vmxnet3: Refine l2 header validation

Validation of l2 header length assumed minimal packet size as
eth_header + 2 * vlan_header regardless of the actual protocol.

This caused crash for valid non-IP packets shorter than 22 bytes, as
'tx_pkt->packet_type' hasn't been assigned for such packets, and
'vmxnet3_on_tx_done_update_stats()' expects it to be properly set.

Refine header length validation in 'vmxnet_tx_pkt_parse_headers'.
Check its return value during packet processing flow.

As a side effect, in case IPv4 and IPv6 header validation failure,
corrupt packets will be dropped.

Signed-off-by: Dana Rubin <dana.rubin@ravellosystems.com>
Signed-off-by: Shmulik Ladkani <shmulik.ladkani@ravellosystems.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

hw/net/vmxnet3.c

diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
index 04159c8..48ced71 100644
--- a/hw/net/vmxnet3.c
+++ b/hw/net/vmxnet3.c
@@ -729,9 +729,7 @@
         }
 
         if (txd.eop) {
-            if (!s->skip_current_tx_pkt) {
-                vmxnet_tx_pkt_parse(s->tx_pkt);
-
+            if (!s->skip_current_tx_pkt && vmxnet_tx_pkt_parse(s->tx_pkt)) {
                 if (s->needs_vlan) {
                     vmxnet_tx_pkt_setup_vlan_header(s->tx_pkt, s->tci);
                 }

hw/net/vmxnet_tx_pkt.c

diff --git a/hw/net/vmxnet_tx_pkt.c b/hw/net/vmxnet_tx_pkt.c
index f7344c4..eb88ddf 100644
--- a/hw/net/vmxnet_tx_pkt.c
+++ b/hw/net/vmxnet_tx_pkt.c
@@ -142,11 +142,24 @@
 
     bytes_read = iov_to_buf(pkt->raw, pkt->raw_frags, 0, l2_hdr->iov_base,
                             ETH_MAX_L2_HDR_LEN);
-    if (bytes_read < ETH_MAX_L2_HDR_LEN) {
+    if (bytes_read < sizeof(struct eth_header)) {
         l2_hdr->iov_len = 0;
         return false;
-    } else {
-        l2_hdr->iov_len = eth_get_l2_hdr_length(l2_hdr->iov_base);
+    }
+
+    l2_hdr->iov_len = sizeof(struct eth_header);
+    switch (be16_to_cpu(PKT_GET_ETH_HDR(l2_hdr->iov_base)->h_proto)) {
+    case ETH_P_VLAN:
+        l2_hdr->iov_len += sizeof(struct vlan_header);
+        break;
+    case ETH_P_DVLAN:
+        l2_hdr->iov_len += 2 * sizeof(struct vlan_header);
+        break;
+    }
+
+    if (bytes_read < l2_hdr->iov_len) {
+        l2_hdr->iov_len = 0;
+        return false;
     }
 
     l3_proto = eth_get_l3_proto(l2_hdr->iov_base, l2_hdr->iov_len);