9832 Original bug discovered as 9560 has friends IPv4 packets coming in as IPv6 creating chaos
Reviewed by: Robert Mustacchi <rm@joyent.com>

*** 19,30 ****
   * CDDL HEADER END
   */
  /*
   * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
-  * Copyright 2017 Joyent, Inc.
   * Copyright 2013 Nexenta Systems, Inc. All rights reserved.
   */
  
  /*
   * MAC data path
   *
--- 19,30 ----
   * CDDL HEADER END
   */
  /*
   * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   * Copyright 2013 Nexenta Systems, Inc. All rights reserved.
+  * Copyright 2019 Joyent, Inc.
   */
  
  /*
   * MAC data path
   *
*** 1713,1722 ****
--- 1713,1723 ----
          uint8_t         nexthdr;
          uint16_t        hdr_len;
          uint32_t        src_val, dst_val;
          boolean_t       modifiable = B_TRUE;
          boolean_t       v6;
+         int             errno;
  
          ASSERT(MBLKL(mp) >= hdrsize);
  
          if (sap == ETHERTYPE_IPV6) {
                  v6 = B_TRUE;
*** 1787,1805 ****
                  /*
                   * Do src based fanout if below tunable is set to B_TRUE or
                   * when mac_ip_hdr_length_v6() fails because of malformed
                   * packets or because mblks need to be concatenated using
                   * pullupmsg().
-                  *
-                  * Perform a version check to prevent parsing weirdness...
                   */
!                 if (IPH_HDR_VERSION(ip6h) != IPV6_VERSION ||
!                     !mac_ip_hdr_length_v6(ip6h, mp->b_wptr, &hdr_len, &nexthdr,
!                     NULL)) {
                          goto src_dst_based_fanout;
                  }
          } else {
                  hdr_len = IPH_HDR_LENGTH(ipha);
                  remlen = ntohs(ipha->ipha_length) - hdr_len;
                  nexthdr = ipha->ipha_protocol;
                  src_val = (uint32_t)ipha->ipha_src;
                  dst_val = (uint32_t)ipha->ipha_dst;
--- 1788,1818 ----
                  /*
                   * Do src based fanout if below tunable is set to B_TRUE or
                   * when mac_ip_hdr_length_v6() fails because of malformed
                   * packets or because mblks need to be concatenated using
                   * pullupmsg().
                   */
!                 errno = mac_ip_hdr_length_v6(ip6h, mp->b_wptr, &hdr_len,
!                     &nexthdr, NULL);
!                 switch (errno) {
!                 case EINVAL:
!                         /* Bad version. */
!                         *indx = 0;
!                         *type = OTH;
!                         return (0);
!                 case 0:
!                         break;
!                 default:
                          goto src_dst_based_fanout;
                  }
          } else {
+                 if (IPH_HDR_VERSION(ipha) != IPV4_VERSION) {
+                         /* Bad version. */
+                         *indx = 0;
+                         *type = OTH;
+                         return (0);
+                 }
                  hdr_len = IPH_HDR_LENGTH(ipha);
                  remlen = ntohs(ipha->ipha_length) - hdr_len;
                  nexthdr = ipha->ipha_protocol;
                  src_val = (uint32_t)ipha->ipha_src;
                  dst_val = (uint32_t)ipha->ipha_dst;