diff --git a/wiretap/libpcap.c b/wiretap/libpcap.c
index 0435e880bc..18026b7596 100644
--- a/wiretap/libpcap.c
+++ b/wiretap/libpcap.c
@@ -55,6 +55,7 @@ typedef struct {
 	guint16	version_major;
 	guint16	version_minor;
 	pcap_variant_t variant;
+	int fcs_len;
 	void *encap_priv;
 } libpcap_t;
 
@@ -87,6 +88,62 @@ static gboolean libpcap_dump_pcap_ss991029(wtap_dumper *wdh,
 static gboolean libpcap_dump_pcap_nokia(wtap_dumper *wdh, const wtap_rec *rec,
     const guint8 *pd, int *err, gchar **err_info);
 
+/*
+ * Subfields of the field containing the link-layer header type.
+ *
+ * Link-layer header types are assigned for both pcap and
+ * pcapng, and the same value must work with both.  In pcapng,
+ * the link-layer header type field in an Interface Description
+ * Block is 16 bits, so only the bottommost 16 bits of the
+ * link-layer header type in a pcap file can be used for the
+ * header type value.
+ *
+ * In libpcap, the upper 16 bits, from the top down, are divided into:
+ *
+ *    A 4-bit "FCS length" field, to allow the FCS length to
+ *    be specified, just as it can be specified in the if_fcslen
+ *    field of the pcapng IDB.  The field is in units of 16 bits,
+ *    i.e. 1 means 16 bits of FCS, 2 means 32 bits of FCS, etc..
+ *
+ *    A reserved bit, which must be zero.
+ *
+ *    An "FCS length present" flag; if 0, the "FCS length" field
+ *    should be ignored, and if 1, the "FCS length" field should
+ *    be used.
+ *
+ *    10 reserved bits, which must be zero.  They were originally
+ *    intended to be used as a "class" field, allowing additional
+ *    classes of link-layer types to be defined, with a class value
+ *    of 0 indicating that the link-layer type is a LINKTYPE_ value.
+ *    A value of 0x224 was, at one point, used by NetBSD to define
+ *    "raw" packet types, with the lower 16 bits containing a
+ *    NetBSD AF_ value; see
+ *
+ *        https://marc.info/?l=tcpdump-workers&m=98296750229149&w=2
+ *
+ *    It's unknown whether those were ever used in capture files,
+ *    or if the intent was just to use it as a link-layer type
+ *    for BPF programs; NetBSD's libpcap used to support them in
+ *    the BPF code generator, but it no longer does so.  If it
+ *    was ever used in capture files, or if classes other than
+ *    "LINKTYPE_ value" are ever useful in capture files, we could
+ *    re-enable this, and use the reserved 16 bits following the
+ *    link-layer type in pcapng files to hold the class information
+ *    there.  (Note, BTW, that LINKTYPE_RAW/DLT_RAW is now being
+ *    interpreted by libpcap, tcpdump, and Wireshark as "raw IP",
+ *    including both IPv4 and IPv6, with the version number in the
+ *    header being checked to see which it is, not just "raw IPv4";
+ *    there are LINKTYPE_IPV4/DLT_IPV4 and LINKTYPE_IPV6/DLT_IPV6
+ *    values if "these are IPv{4,6} and only IPv{4,6} packets"
+ *    types are needed.)
+ */
+#define LT_LINKTYPE(x)			((x) & 0x0000FFFF)
+#define LT_CLASS(x)			(((x) & 0x3FFF0000) >> 16)
+#define LT_CLASS_LINKTYPE		0x0000
+#define LT_FCS_LENGTH_PRESENT(x)	((x) & 0x04000000)
+#define LT_FCS_LENGTH(x)		(((x) & 0xF0000000) >> 28)
+#define LT_FCS_DATALINK_EXT(x)		(((x) & 0xF) << 28) | 0x04000000)
+
 /*
  * Private file type/subtype values; pcap and nanosecond-resolution
  * pcap are imported from wiretap/file_access.c.
@@ -359,51 +416,44 @@ wtap_open_return_val libpcap_open(wtap *wth, int *err, gchar **err_info)
 			break;
 		}
 	}
+
 	/*
-	 * Map the "network" field from the header to a Wiretap
-	 * encapsulation.
-	 *
-	 * Link-layer header types are assigned for both pcap and
-	 * pcapng, and the same value must work with both.  In pcapng,
-	 * the link-layer header type field in an Interface Description
-	 * Block is 16 bits, so only the bottommost 16 bits of the
-	 * link-layer header type in a pcap file can be used for the
-	 * header type value.
-	 *
-	 * In libpcap, the upper 16 bits are divided into:
-	 *
-	 *    A "class" field, to support non-standard link-layer
-	 *    header types; class 0 is for standard header types,
-	 *    class 0x224 was reserved for a NetBSD feature, and
-	 *    all other class values are reserved.  That is in the
-	 *    lower 10 bits of the upper 16 bits.
-	 *
-	 *    An "FCS length" field, to allow the FCS length to
-	 *    be specified, just as it can be specified in the
-	 *    if_fcslen field of the pcapng IDB.  That is in the
-	 *    topmost 4 bits of the upper 16 bits.  The field is
-	 *    in units of 16 bits, i.e. 1 means 16 bits of FCS,
-	 *    2 means 32 bits of FCS, etc..
-	 *
-	 *    An "FCS length present" flag; if 0, the "FCS length"
-	 *    field should be ignored, and if 1, the "FCS length"
-	 *    field should be used.  That is in the bit just above
-	 *    the "class" field.
-	 *
-	 *    The one remaining bit is reserved.
-	 *
-	 * We ignore the FCS information and reserved bit; we include
-	 * the "class" field, in case there's ever a need to implement
-	 * it - currently, any link-layer header type with a non-zero
-	 * class value will fail.
+	 * Check the "class" field of the "network" field in the header.
 	 */
-	wth->file_encap = wtap_pcap_encap_to_wtap_encap(hdr.network & 0x03FFFFFF);
-	if (wth->file_encap == WTAP_ENCAP_UNKNOWN) {
+	switch (LT_CLASS(hdr.network)) {
+
+	case LT_CLASS_LINKTYPE:
+		/*
+		 * Map the link-layer type from the "network" field in
+		 * the header to a Wiretap encapsulation.
+		 */
+		wth->file_encap = wtap_pcap_encap_to_wtap_encap(LT_LINKTYPE(hdr.network));
+		if (wth->file_encap == WTAP_ENCAP_UNKNOWN) {
+			*err = WTAP_ERR_UNSUPPORTED;
+			*err_info = ws_strdup_printf("pcap: network type %u unknown or unsupported",
+			    hdr.network);
+			return WTAP_OPEN_ERROR;
+		}
+		break;
+
+	default:
 		*err = WTAP_ERR_UNSUPPORTED;
-		*err_info = ws_strdup_printf("pcap: network type %u unknown or unsupported",
-		    hdr.network);
+		*err_info = ws_strdup_printf("pcap: network type class 0x%04x not supported",
+		    LT_CLASS(hdr.network));
 		return WTAP_OPEN_ERROR;
 	}
+
+	/*
+	 * Extract the FCS information, if present.
+	 */
+	libpcap->fcs_len = -1;
+	if (LT_FCS_LENGTH_PRESENT(hdr.network)) {
+		/*
+		 * We have an FCS length.
+		 */
+		libpcap->fcs_len = LT_FCS_LENGTH(hdr.network) * 16;
+	}
+
 	libpcap->encap_priv = NULL;
 
 	/*
@@ -967,7 +1017,7 @@ libpcap_read_packet(wtap *wth, FILE_T fh, wtap_rec *rec,
 		return FALSE;	/* failed */
 
 	pcap_read_post_process(is_nokia, wth->file_encap, rec,
-	    ws_buffer_start_ptr(buf), libpcap->byte_swapped, -1);
+	    ws_buffer_start_ptr(buf), libpcap->byte_swapped, libpcap->fcs_len);
 	return TRUE;
 }