Get rid of the PCAP_ENCAP_ values - if an application uses them, that

application won't build with any other version of libpcap, which means
that a lot of applications won't use them.  In addition,
"pcap_linktype()" needs to return DLT_ values, so that platforms that
build libpcap as a shared library won't break binary compatibility if
they update to this version of libpcap.

Instead, we map from DLT_ values to LINKTYPE_ values when writing
savefiles, and map from LINKTYPE_ values to DLT_ values when reading
savefiles, so that savefiles don't have platform-dependent DLT_ values
in the header as the link type, they have platform-independent LINKTYPE_
values.

This means we don't need to make DLT_ATM_RFC1483, DLT_RAW, etc. have
platform-independent values starting at 100 - only the values in the
savefile header need to be like that.

bpf/net/bpf.h

@@ -37,7 +37,7 @@
  *
  *      @(#)bpf.h       7.1 (Berkeley) 5/7/91
  *
- * @(#) $Header: /tcpdump/master/libpcap/bpf/net/Attic/bpf.h,v 1.39 2000-09-17 04:04:39 guy Exp $ (LBL)
+ * @(#) $Header: /tcpdump/master/libpcap/bpf/net/Attic/bpf.h,v 1.40 2000-10-12 03:54:02 guy Exp $ (LBL)
  */
 
 #ifndef BPF_MAJOR_VERSION
@@ -160,6 +160,9 @@ struct bpf_hdr {
 
 /*
  * Data-link level type codes.
+ */
+
+/*
  * These are the types that are the same on all platforms; on other
  * platforms, a <net/bpf.h> should be supplied that defines the additional
  * DLT_* codes appropriately for that platform (the BSDs, for example,
@@ -178,40 +181,57 @@ struct bpf_hdr {
 #define DLT_SLIP	8	/* Serial Line IP */
 #define DLT_PPP		9	/* Point-to-point Protocol */
 #define DLT_FDDI	10	/* FDDI */
-#define DLT_ATM_CLIP	19	/* Linux Classical-IP over ATM */
 
 /*
- * These are the values that were traditionally defined in <net/bpf.h>,
- * but that are not the same on all platforms; if they are not already
- * defined (e.g., defined above because this is a BSD that defines them
- * for use in its kernel), we define them to have the appropriate
- * PCAP_ENCAP_* value from <pcap.h>, so that programs using those DLT_
- * codes will continue to compile and will be able to read capture files
- * from the current version of libpcap.
+ * These are values from the traditional libpcap "bpf.h".
+ * Ports of this to particular platforms should replace these definitions
+ * with the ones appropriate to that platform, if the values are
+ * different on that platform.
  */
-#ifndef DLT_ATM_RFC1483
-#define DLT_ATM_RFC1483	100	/* LLC/SNAP encapsulated atm */
-#endif
-#ifndef DLT_RAW
-#define DLT_RAW		101	/* raw IP */
-#endif
+#define DLT_ATM_RFC1483	11	/* LLC/SNAP encapsulated atm */
+#define DLT_RAW		12	/* raw IP */
+
+/*
+ * These are values from BSD/OS's "bpf.h".
+ * These are not the same as the values from the traditional libpcap
+ * "bpf.h"; however, these values shouldn't be generated by any
+ * OS other than BSD/OS, so the correct values to use here are the
+ * BSD/OS values.
+ *
+ * Platforms that have already assigned these values to other
+ * DLT_ codes, however, should give these codes the values
+ * from that platform, so that programs that use these codes will
+ * continue to compile - even though they won't correctly read
+ * files of these types.
+ */
+#define DLT_SLIP_BSDOS	15	/* BSD/OS Serial Line IP */
+#define DLT_PPP_BSDOS	16	/* BSD/OS Point-to-point Protocol */
+
+#define DLT_ATM_CLIP	19	/* Linux Classical-IP over ATM */
 
 /*
- * NOTE: these two values were defined by LBL libpcap, but with values
- * that didn't seem to correspond to the values that were used in BSD/OS;
- * neither of them are, as far as I know, used in any kernel, so they
- * should not be defined above.  We therefore don't bother checking to
- * see if they're already defined.
+ * This value is defined by NetBSD; other platforms should refrain from
+ * using it for other purposes, so that NetBSD savefiles with a link
+ * type of 50 can be read as this type on all platforms.
  */
-#define DLT_SLIP_BSDOS	102	/* BSD/OS Serial Line IP */
-#define DLT_PPP_BSDOS	103	/* BSD/OS Point-to-point Protocol */
+#define DLT_PPP_SERIAL	50	/* PPP over serial with HDLC encapsulation */
 
 /*
- * This value was defined by libpcap 0.5; we now use it as a DLT_* value
- * solely for backwards compatibility - new programs should use
- * PCAP_ENCAP_C_HDLC instead.
+ * This value was defined by libpcap 0.5; platforms that have defined
+ * it with a different value should define it here with that value -
+ * a link type of 104 in a save file will be mapped to DLT_C_HDLC,
+ * whatever value that happens to be, so programs will correctly
+ * handle files with that link type regardless of the value of
+ * DLT_C_HDLC.
+ *
+ * The name DLT_C_HDLC was used by BSD/OS; we use that name for source
+ * compatibility with programs written for BSD/OS.
+ *
+ * libpcap 0.5 defined it as DLT_CHDLC; we define DLT_CHDLC as well,
+ * for source compatibility with programs written for libpcap 0.5.
  */
-#define DLT_CHDLC	104	/* Cisco HDLC */
+#define DLT_C_HDLC	104	/* Cisco HDLC */
+#define DLT_CHDLC	DLT_C_HDLC
 
 /*
  * The instruction encondings.