I *always* forget svn add :(

diff --git a/networking/udhcp/domain_codec.c b/networking/udhcp/domain_codec.c
new file mode 100644 (file)
index 0000000..6e16dde
--- /dev/null
+++ b/networking/udhcp/domain_codec.c
@@ -0,0 +1,205 @@
+/* vi: set sw=4 ts=4: */
+
+/* RFC1035 domain compression routines (C) 2007 Gabriel Somlo <somlo at cmu.edu>
+ *
+ * Loosely based on the isc-dhcpd implementation by dhankins@isc.org
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#if ENABLE_FEATURE_RFC3397
+
+#include "common.h"
+#include "options.h"
+
+#define NS_MAXDNAME  1025      /* max domain name length */
+#define NS_MAXCDNAME  255      /* max compressed domain name length */
+#define NS_MAXLABEL    63      /* max label length */
+#define NS_MAXDNSRCH    6      /* max domains in search path */
+#define NS_CMPRSFLGS 0xc0      /* name compression pointer flag */
+
+
+/* expand a RFC1035-compressed list of domain names "cstr", of length "clen";
+ * returns a newly allocated string containing the space-separated domains,
+ * prefixed with the contents of string pre, or NULL if an error occurs.
+ */
+char *dname_dec(const uint8_t *cstr, int clen, const char *pre)
+{
+       const uint8_t *c;
+       int crtpos, retpos, depth, plen = 0, len = 0;
+       char *dst = NULL;
+
+       if (!cstr)
+               return NULL;
+
+       if (pre)
+               plen = strlen(pre);
+
+       /* We make two passes over the cstr string. First, we compute
+        * how long the resulting string would be. Then we allocate a
+        * new buffer of the required length, and fill it in with the
+        * expanded content. The advantage of this approach is not
+        * having to deal with requiring callers to supply their own
+        * buffer, then having to check if it's sufficiently large, etc.
+        */
+
+       while (!dst) {
+
+               if (len > 0) {  /* second pass? allocate dst buffer and copy pre */
+                       dst = xmalloc(len + plen);
+                       memcpy(dst, pre, plen);
+               }
+
+               crtpos = retpos = depth = len = 0;
+
+               while (crtpos < clen) {
+                       c = cstr + crtpos;
+
+                       if ((*c & NS_CMPRSFLGS) != 0) { /* pointer */
+                               if (crtpos + 2 > clen)          /* no offset to jump to? abort */
+                                       return NULL;
+                               if (retpos == 0)                        /* toplevel? save return spot */
+                                       retpos = crtpos + 2;
+                               depth++;
+                               crtpos = ((*c & 0x3f) << 8) | (*(c + 1) & 0xff); /* jump */
+                       } else if (*c) {                        /* label */
+                               if (crtpos + *c + 1 > clen)             /* label too long? abort */
+                                       return NULL;
+                               if (dst)
+                                       memcpy(dst + plen + len, c + 1, *c);
+                               len += *c + 1;
+                               crtpos += *c + 1;
+                               if (dst)
+                                       *(dst + plen + len - 1) = '.';
+                       } else {                                        /* null: end of current domain name */
+                               if (retpos == 0) {                      /* toplevel? keep going */
+                                       crtpos++;
+                               } else {                                        /* return to toplevel saved spot */
+                                       crtpos = retpos;
+                                       retpos = depth = 0;
+                               }
+                               if (dst)
+                                       *(dst + plen + len - 1) = ' ';
+                       }
+
+                       if (depth > NS_MAXDNSRCH || /* too many jumps? abort, it's a loop */
+                               len > NS_MAXDNAME * NS_MAXDNSRCH) /* result too long? abort */
+                               return NULL;
+               }
+
+               if (!len)                       /* expanded string has 0 length? abort */
+                       return NULL;
+
+               if (dst)
+                       *(dst + plen + len - 1) = '\0';
+       }
+
+       return dst;
+}
+
+/* Convert a domain name (src) from human-readable "foo.blah.com" format into
+ * RFC1035 encoding "\003foo\004blah\003com\000". Return allocated string, or
+ * NULL if an error occurs.
+ */
+static uint8_t *convert_dname(const char *src)
+{
+       uint8_t c, *res, *lp, *rp;
+       int len;
+
+       res = xmalloc(strlen(src) + 2);
+       rp = lp = res;
+       rp++;
+
+       for (;;) {
+               c = (uint8_t)*src++;
+               if (c == '.' || c == '\0') {    /* end of label */
+                       len = rp - lp - 1;
+                       /* label too long, too short, or two '.'s in a row? abort */
+                       if (len > NS_MAXLABEL || len == 0 || (c == '.' && *src == '.')) {
+                               free(res);
+                               return NULL;
+                       }
+                       *lp = len;
+                       lp = rp++;
+                       if (c == '\0' || *src == '\0')  /* end of dname */
+                               break;
+               } else {
+                       if (c >= 0x41 && c <= 0x5A)             /* uppercase? convert to lower */
+                               c += 0x20;
+                       *rp++ = c;
+               }
+       }
+
+       *lp = 0;
+       if (rp - res > NS_MAXCDNAME) {  /* dname too long? abort */
+               free(res);
+               return NULL;
+       }
+       return res;
+}
+
+/* returns the offset within cstr at which dname can be found, or -1
+ */
+static int find_offset(const uint8_t *cstr, int clen, const uint8_t *dname)
+{
+       const uint8_t *c, *d;
+       int off, inc;
+
+       /* find all labels in cstr */
+       off = 0;
+       while (off < clen) {
+               c = cstr + off;
+
+               if ((*c & NS_CMPRSFLGS) != 0) { /* pointer, skip */
+                       off += 2;
+               } else if (*c) {        /* label, try matching dname */
+                       inc = *c + 1;
+                       d = dname;
+                       while (*c == *d && memcmp(c + 1, d + 1, *c) == 0) {
+                               if (*c == 0)    /* match, return offset */
+                                       return off;
+                               d += *c + 1;
+                               c += *c + 1;
+                               if ((*c & NS_CMPRSFLGS) != 0)   /* pointer, jump */
+                                       c = cstr + (((*c & 0x3f) << 8) | (*(c + 1) & 0xff));
+                       }
+                       off += inc;
+               } else {        /* null, skip */
+                       off++;
+               }
+       }
+
+       return -1;
+}
+
+/* computes string to be appended to cstr so that src would be added to
+ * the compression (best case, it's a 2-byte pointer to some offset within
+ * cstr; worst case, it's all of src, converted to rfc3011 format).
+ * The computed string is returned directly; its length is returned via retlen;
+ * NULL and 0, respectively, are returned if an error occurs.
+ */
+uint8_t *dname_enc(const uint8_t *cstr, int clen, const char *src, int *retlen)
+{
+       uint8_t *d, *dname;
+       int off;
+
+       dname = convert_dname(src);
+       if (dname == NULL) {
+               *retlen = 0;
+               return NULL;
+       }
+
+       for (d = dname; *d != 0; d += *d + 1) {
+               off = find_offset(cstr, clen, d);
+               if (off >= 0) { /* found a match, add pointer and terminate string */
+                       *d++ = NS_CMPRSFLGS;
+                       *d = off;
+                       break;
+               }
+       }
+
+       *retlen = d - dname + 1;
+       return dname;
+}              
+
+#endif /* ENABLE_FEATURE_RFC3397 */