7388 Support DHCP Client FQDN. Allow IAID/DUID for all v4.

@@ -19,10 +19,11 @@
  * CDDL HEADER END
  */
 /*
  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
+ * Copyright (c) 2016, Chris Fraire <cfraire@me.com>.
  */
 
 #include <string.h>
 #include <sys/types.h>
 #include <stdlib.h>

@@ -411,38 +412,27 @@
 void *
 add_pkt_opt(dhcp_pkt_t *dpkt, uint_t opt_type, const void *opt_val,
     uint_t opt_len)
 {
         uchar_t         *raw_pkt;
-        int             req_len;
+        size_t          req_len;
         void            *optr;
 
         raw_pkt = (uchar_t *)dpkt->pkt;
         optr = raw_pkt + dpkt->pkt_cur_len;
         if (dpkt->pkt_isv6) {
-                dhcpv6_option_t d6o;
+                req_len = opt_len + sizeof (dhcpv6_option_t);
 
-                req_len = opt_len + sizeof (d6o);
-
                 if (dpkt->pkt_cur_len + req_len > dpkt->pkt_max_len) {
                         dhcpmsg(MSG_WARNING,
                             "add_pkt_opt: not enough room for v6 option %u in "
                             "packet (%u + %u > %u)", opt_type,
                             dpkt->pkt_cur_len, req_len, dpkt->pkt_max_len);
                         return (NULL);
                 }
-                d6o.d6o_code = htons(opt_type);
-                d6o.d6o_len = htons(opt_len);
-                (void) memcpy(&raw_pkt[dpkt->pkt_cur_len], &d6o, sizeof (d6o));
-                dpkt->pkt_cur_len += sizeof (d6o);
-                if (opt_len > 0) {
-                        (void) memcpy(&raw_pkt[dpkt->pkt_cur_len], opt_val,
-                            opt_len);
-                        dpkt->pkt_cur_len += opt_len;
-                }
         } else {
-                req_len = opt_len + 2; /* + 2 for code & length bytes */
+                req_len = opt_len + DHCP_OPT_META_LEN;
 
                 /* CD_END and CD_PAD options don't have a length field */
                 if (opt_type == CD_END || opt_type == CD_PAD) {
                         req_len = 1;
                 } else if (opt_val == NULL) {

@@ -455,23 +445,66 @@
                         dhcpmsg(MSG_WARNING,
                             "add_pkt_opt: not enough room for v4 option %u in "
                             "packet", opt_type);
                         return (NULL);
                 }
+        }
 
-                raw_pkt[dpkt->pkt_cur_len++] = opt_type;
+        req_len = encode_dhcp_opt(&raw_pkt[dpkt->pkt_cur_len], dpkt->pkt_isv6,
+            opt_type, opt_val, opt_len);
+        dpkt->pkt_cur_len += req_len;
 
-                if (req_len > 1) {
-                        raw_pkt[dpkt->pkt_cur_len++] = opt_len;
-                        if (opt_len > 0) {
-                                (void) memcpy(&raw_pkt[dpkt->pkt_cur_len],
-                                    opt_val, opt_len);
-                                dpkt->pkt_cur_len += opt_len;
+        return (optr);
+}
+
+/*
+ * encode_dhcp_opt(): sets the fields of an allocated DHCP option buffer
+ *
+ *   input: void *: the buffer allocated for enough space for
+ *                      (DHCPv6) dhcpv6_option_t and value, or for (DHCPv4) opt_type +
+ *                      length + value (length/value are skipped for CD_END or
+ *                      CD_PAD);
+ *          boolean_t: a value indicating whether DHCPv6 or not;
+ *          uint_t: the type of option being added;
+ *          const void *: the value of that option;
+ *          uint_t: the length of the value of the option
+ *  output: size_t: the number of bytes written starting at opt.
+ */
+
+size_t
+encode_dhcp_opt(void *dopt, boolean_t isv6, uint_t opt_type,
+    const void *opt_val, uint_t opt_len)
+{
+        boolean_t do_copy_value = B_FALSE;
+        size_t res_len = 0;
+        uint8_t *pval;
+
+        if (isv6) {
+                dhcpv6_option_t d6o;
+                d6o.d6o_code = htons(opt_type);
+                d6o.d6o_len = htons(opt_len);
+                (void) memcpy(dopt, &d6o, sizeof (d6o));
+                res_len += sizeof (d6o);
+
+                do_copy_value = B_TRUE;
+        } else {
+                pval = (uint8_t *)dopt;
+                pval[res_len++] = opt_type;
+
+                if (opt_type != CD_END && opt_type != CD_PAD) {
+                        pval[res_len++] = opt_len;
+                        do_copy_value = B_TRUE;
                         }
                 }
+
+        pval = (uint8_t *)dopt + res_len;
+        if (do_copy_value && opt_len > 0) {
+                (void) memcpy(pval, opt_val, opt_len);
+                res_len += opt_len;
         }
-        return (optr);
+
+        return (res_len);
 }
 
 /*
  * add_pkt_subopt(): adds an option to a dhcp_pkt_t option.  DHCPv6-specific,
  *                   but could be extended to IPv4 DHCP if necessary.  Assumes