+ /*
+ * Some printers want to get back at the link level addresses,
+ * and/or check that they're not walking off the end of the packet.
+ * Rather than pass them all the way down, we set these globals. */
+
+ packetp = p;
+ snapend = p + caplen;
+
+#if 0
+ /*
+ * XXX: seems to assume that there are 2 octets prepended to an
+ * actual PPP frame. The 1st octet looks like Input/Output flag
+ * while 2nd octet is unknown, at least to me
+ *
+ * That was what the original tcpdump code did.
+ *
+ * FreeBSD's "if_ppp.c" *does* set the first octet to 1 for outbound
+ * packets and 0 for inbound packets - but only if the
+ * protocol field has the 0x8000 bit set (i.e., it's a network
+ * control protocol); it does so before running the packet through
+ * "bpf_filter" to see if it should be discarded, and to see
+ * if we should update the time we sent the most recent packet...
+ *
+ * ...but it puts the original address field back after doing
+ * so.
+ *
+ * NetBSD's "if_ppp.c" doesn't set the first octet in that fashion.
+ *
+ * I don't know if any PPP implementation handed up to a BPF
+ * device packets with the first octet being 1 for outbound and
+ * whether that ever needs to be checked or not.
+ *
+ * Note that NetBSD has a DLT_PPP_SERIAL, which it uses for PPP,
+ * and its tcpdump appears to assume that the frame always
+ * begins with an address field and a control field, and that
+ * the address field might be 0x0f or 0x8f, for Cisco
+ * point-to-point with HDLC framing as per section 4.3.1 of RFC
+ * 1547, as well as 0xff, for PPP in HDLC-like framing as per
+ * RFC 1662.
+ *
+ * (Is the Cisco framing in question what DLT_C_HDLC, in
+ * BSD/OS, is?)
+ */
+ if (eflag)
+ printf("%c %4d %02x ", p[0] ? 'O' : 'I', length, p[1]);
+#endif
+
+ ppp_print(p, length);
+
+ if (xflag)
+ default_print(p, caplen);
+out:
+ putchar('\n');
+}
+
+/*
+ * PPP I/F printer to use if we know that RFC 1662-style PPP in HDLC-like
+ * framing, or Cisco PPP with HDLC framing as per section 4.3.1 of RFC 1547,
+ * is being used (i.e., we don't check for PPP_ADDRESS and PPP_CONTROL,
+ * discard them *if* those are the first two octets, and parse the remaining
+ * packet as a PPP packet, as "ppp_print()" does).
+ *
+ * This handles, for example, DLT_PPP_SERIAL in NetBSD.
+ */
+void
+ppp_hdlc_if_print(u_char *user, const struct pcap_pkthdr *h,
+ register const u_char *p)
+{
+ register u_int length = h->len;
+ register u_int caplen = h->caplen;
+ u_int proto;
+
+ if (caplen < 2) {
+ printf("[|ppp]");
+ goto out;
+ }
+
projects / tcpdump / blobdiff