Decode DHCP option 52 (Option Overload). Decode the options embedded

in the sname and file options as needed.  Thanks to Tedd Frechette for
the sample capture.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@6345 f5534014-38df-0310-8fa8-9805f1628bb7

diff --git a/packet-bootp.c b/packet-bootp.c
index 22ef4ef0b7f2c52d331990933510eedda045b3e0..3c3edf55a5a6570b0e1f82ec8d8c1e2e408ce907 100644 (file)
--- a/packet-bootp.c
+++ b/packet-bootp.c
@@ -2,7 +2,7 @@
  * Routines for BOOTP/DHCP packet disassembly
  * Gilbert Ramirez <gram@alumni.rice.edu>
  *
- * $Id: packet-bootp.c,v 1.70 2002/08/28 21:00:08 jmayer Exp $
+ * $Id: packet-bootp.c,v 1.71 2002/09/28 04:12:38 gerald Exp $
  *
  * The information used comes from:
  * RFC  951: Bootstrap Protocol
@@ -134,6 +134,18 @@ get_dhcp_type(guint8 byte)
 /* DHCP Authentication Replay Detection Methods */
 #define AUTHEN_RDM_MONOTONIC_COUNTER   0x00
 
+/* DHCP Option Overload (option code 52) */
+#define OPT_OVERLOAD_FILE              1
+#define OPT_OVERLOAD_SNAME             2
+#define OPT_OVERLOAD_BOTH              3
+
+/* Server name and boot file offsets and lengths */
+#define SERVER_NAME_OFFSET             44
+#define SERVER_NAME_LEN                64
+#define FILE_NAME_OFFSET               108
+#define FILE_NAME_LEN                  128
+#define VENDOR_INFO_OFFSET             236
+
 /* Returns the number of bytes consumed by this option. */
 static int
 bootp_option(tvbuff_t *tvb, proto_tree *bp_tree, int voff, int eoff,
@@ -147,11 +159,13 @@ bootp_option(tvbuff_t *tvb, proto_tree *bp_tree, int voff, int eoff,
        guchar                  byte;
        int                     i,optp, consumed;
        gulong                  time_secs;
-       proto_tree              *v_tree;
+       proto_tree              *v_tree, *o52tree;
        proto_item              *vti;
        guint8                  protocol;
        guint8                  algorithm;
        guint8                  rdm;
+       int                     o52voff, o52eoff;
+       gboolean                o52at_end;
 
        static const value_string nbnt_vals[] = {
            {0x1,   "B-node" },
@@ -173,6 +187,12 @@ bootp_option(tvbuff_t *tvb, proto_tree *bp_tree, int voff, int eoff,
            {AUTHEN_RDM_MONOTONIC_COUNTER, "Monotonically-increasing counter" },
            {0,                            NULL     } };
 
+       static const value_string opt_overload_vals[] = {
+           { OPT_OVERLOAD_FILE,  "Boot file name holds options",                },
+           { OPT_OVERLOAD_SNAME, "Server host name holds options",              },
+           { OPT_OVERLOAD_BOTH,  "Boot file and server host names hold options" },
+           { 0,                  NULL                                           } };
+
        static struct opt_info opt[] = {
                /*   0 */ { "Padding",                                                          none },
                /*   1 */ { "Subnet Mask",                                                      ipv4 },
@@ -562,6 +582,51 @@ bootp_option(tvbuff_t *tvb, proto_tree *bp_tree, int voff, int eoff,
                                    "Unknown (0x%02x)"));
                break;
 
+       case 52:        /* Option Overload */
+               byte = tvb_get_guint8(tvb, voff+2);
+               vti = proto_tree_add_text(bp_tree, tvb, voff, consumed,
+                       "Option %d: %s = %s", code, text,
+                       val_to_str(byte, opt_overload_vals,
+                           "Unknown (0x%02x)"));
+                           
+               /* Just in case we find an option 52 in sname or file */
+               if (voff > VENDOR_INFO_OFFSET && byte >= 1 && byte <= 3) {
+                       o52tree = proto_item_add_subtree(vti, ett_bootp_option);
+                       if (byte == 1 || byte == 3) {   /* 'file' */
+                               vti = proto_tree_add_text (o52tree, tvb,
+                                       FILE_NAME_OFFSET, FILE_NAME_LEN,
+                                       "Boot file name option overload");
+                               v_tree = proto_item_add_subtree(vti, ett_bootp_option);
+                               o52voff = FILE_NAME_OFFSET;
+                               o52eoff = FILE_NAME_OFFSET + FILE_NAME_LEN;
+                               o52at_end = FALSE;
+                               while (o52voff < o52eoff && !o52at_end) {
+                                       o52voff += bootp_option(tvb, v_tree, o52voff,
+                                               o52eoff, FALSE, &o52at_end,
+                                               dhcp_type_p, vendor_class_id_p);
+                               }
+                       }
+                       if (byte == 2 || byte == 3) {   /* 'sname' */
+                               vti = proto_tree_add_text (o52tree, tvb,
+                                       SERVER_NAME_OFFSET, SERVER_NAME_LEN, 
+                                       "Server host name option overload");
+                               v_tree = proto_item_add_subtree(vti, ett_bootp_option);
+                               o52voff = SERVER_NAME_OFFSET;
+                               o52eoff = SERVER_NAME_OFFSET + SERVER_NAME_LEN;
+                               o52at_end = FALSE;
+                               while (o52voff < o52eoff && !o52at_end) {
+                                       o52voff += bootp_option(tvb, v_tree, o52voff,
+                                               o52eoff, FALSE, &o52at_end,
+                                               dhcp_type_p, vendor_class_id_p);
+                               }
+                       }
+               }
+
+/*             protocol = tvb_get_guint8(tvb, voff+2);
+               proto_tree_add_text(v_tree, tvb, voff+2, 1, "Protocol: %s (%u)",
+                                   val_to_str(protocol, authen_protocol_vals, "Unknown"),
+                                   protocol); */
+               break;
        case 53:        /* DHCP Message Type */
                proto_tree_add_text(bp_tree, tvb, voff, 3, "Option %d: %s = DHCP %s",
                        code, text, get_dhcp_type(tvb_get_guint8(tvb, voff+2)));
@@ -1196,29 +1261,33 @@ dissect_bootp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
                /* The server host name is optional */
                if (tvb_get_guint8(tvb, 44) != '\0') {
                        proto_tree_add_item(bp_tree, hf_bootp_server, tvb,
-                                                  44, 64, FALSE);
+                                                  SERVER_NAME_OFFSET, 
+                                                  SERVER_NAME_LEN, FALSE);
                }
                else {
                        proto_tree_add_string_format(bp_tree, hf_bootp_server, tvb,
-                                                  44, 64,
-                                                  tvb_get_ptr(tvb, 44, 1),
+                                                  SERVER_NAME_OFFSET, 
+                                                  SERVER_NAME_LEN,
+                                                  tvb_get_ptr(tvb, SERVER_NAME_OFFSET, 1),
                                                   "Server host name not given");
                }
 
                /* Boot file */
                if (tvb_get_guint8(tvb, 108) != '\0') {
                        proto_tree_add_item(bp_tree, hf_bootp_file, tvb,
-                                                  108, 128, FALSE);
+                                                  FILE_NAME_OFFSET,
+                                                  FILE_NAME_LEN, FALSE);
                }
                else {
                        proto_tree_add_string_format(bp_tree, hf_bootp_file, tvb,
-                                                  108, 128,
-                                                  tvb_get_ptr(tvb, 108, 1),
+                                                  FILE_NAME_OFFSET,
+                                                  FILE_NAME_LEN,
+                                                  tvb_get_ptr(tvb, FILE_NAME_OFFSET, 1),
                                                   "Boot file name not given");
                }
        }
 
-       voff = 236;
+       voff = VENDOR_INFO_OFFSET;
 
        /* rfc2132 says it SHOULD exist, not that it MUST exist */
        if (tvb_bytes_exist(tvb, voff, 4)) {