Do packet length checks iff they're necessary.

They're not necessary for most hardware; remove the unnecessary checks,
and add comments indicating why they're not necessary (or fix the
"maximum value of actual_octets is" part of the comment).

They *are* necessary for Series III hardware; put in the check.

Change-Id: Idd64a74099d5cf7398a2ddb850442e53c9206724
Reviewed-on: https://code.wireshark.org/review/21491
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 20 insertions, 18 deletions

diff --git a/wiretap/vwr.c b/wiretap/vwr.c
index 23b276ec7a..10695f49a1 100644
--- a/wiretap/vwr.c
+++ b/wiretap/vwr.c
@@ -1227,7 +1227,7 @@ static gboolean vwr_read_s1_W_rec(vwr_t *vwr, struct wtap_pkthdr *phdr,
      *
      * We include the length of the metadata headers in the packet lengths.
      *
-     * The maximum value of actual_octets is 65535, which, even after
+     * The maximum value of actual_octets is 8191, which, even after
      * adding the lengths of the metadata headers, is less than
      * WTAP_MAX_PACKET_SIZE will ever be, so we don't need to check it.
      */
@@ -1615,20 +1615,13 @@ static gboolean vwr_read_s2_W_rec(vwr_t *vwr, struct wtap_pkthdr *phdr,
      * Fill up the per-packet header.
      *
      * We include the length of the metadata headers in the packet lengths.
+     *
+     * The maximum value of actual_octets is 8191, which, even after
+     * adding the lengths of the metadata headers, is less than
+     * WTAP_MAX_PACKET_SIZE will ever be, so we don't need to check it.
      */
     phdr->len = STATS_COMMON_FIELDS_LEN + EXT_WLAN_FIELDS_LEN + actual_octets;
     phdr->caplen = STATS_COMMON_FIELDS_LEN + EXT_WLAN_FIELDS_LEN + actual_octets;
-    if (phdr->caplen > WTAP_MAX_PACKET_SIZE) {
-        /*
-         * Probably a corrupt capture file; return an error,
-         * so that our caller doesn't blow up trying to allocate
-         * space for an immensely-large packet.
-         */
-        *err_info = g_strdup_printf("vwr: File has %u-byte packet, bigger than maximum of %u",
-                                    phdr->caplen, WTAP_MAX_PACKET_SIZE);
-        *err = WTAP_ERR_BAD_FILE;
-        return FALSE;
-    }
 
     phdr->ts.secs   = (time_t)s_sec;
     phdr->ts.nsecs  = (int)(s_usec * 1000);
@@ -2092,6 +2085,17 @@ static gboolean vwr_read_s3_W_rec(vwr_t *vwr, struct wtap_pkthdr *phdr,
             phdr->len = OCTO_TIMESTAMP_FIELDS_LEN + OCTO_LAYER1TO4_LEN + actual_octets;
             phdr->caplen = OCTO_TIMESTAMP_FIELDS_LEN + OCTO_LAYER1TO4_LEN + actual_octets;
         }
+        if (phdr->caplen > WTAP_MAX_PACKET_SIZE) {
+            /*
+             * Probably a corrupt capture file; return an error,
+             * so that our caller doesn't blow up trying to allocate
+             * space for an immensely-large packet.
+             */
+            *err_info = g_strdup_printf("vwr: File has %u-byte packet, bigger than maximum of %u",
+                                        phdr->caplen, WTAP_MAX_PACKET_SIZE);
+            *err = WTAP_ERR_BAD_FILE;
+            return FALSE;
+        }
 
         phdr->ts.secs   = (time_t)s_sec;
         phdr->ts.nsecs  = (int)(s_usec * 1000);
@@ -2478,12 +2482,6 @@ static gboolean vwr_read_rec_data_ethernet(vwr_t *vwr, struct wtap_pkthdr *phdr,
         return FALSE;
     }
 
-    /*
-     * The maximum value of actual_octets is 65535, which, even after
-     * adding the lengths of the metadata headers, is less than
-     * WTAP_MAX_PACKET_SIZE will ever be, so we don't need to check it.
-     */
-
     vc_id = pntoh16(&s_ptr[vwr->VCID_OFF]) & vwr->VCID_MASK;
     flow_seq   = s_ptr[vwr->FLOWSEQ_OFF];
     frame_type = pntoh32(&s_ptr[vwr->FRAME_TYPE_OFF]);
@@ -2596,6 +2594,10 @@ static gboolean vwr_read_rec_data_ethernet(vwr_t *vwr, struct wtap_pkthdr *phdr,
      * Fill up the per-packet header.
      *
      * We include the length of the metadata headers in the packet lengths.
+     *
+     * The maximum value of actual_octets is 65535, which, even after
+     * adding the lengths of the metadata headers, is less than
+     * WTAP_MAX_PACKET_SIZE will ever be, so we don't need to check it.
      */
     phdr->len = STATS_COMMON_FIELDS_LEN + EXT_ETHERNET_FIELDS_LEN + actual_octets;
     phdr->caplen = STATS_COMMON_FIELDS_LEN + EXT_ETHERNET_FIELDS_LEN + actual_octets;