Add dn resolution function

Signed-off-by: songlinzhang <songlinzhang@xiaomi.com>

include/resolv.h

@@ -42,6 +42,14 @@ int b64_ntop(FAR const unsigned char *src, size_t srclen,
 int b64_pton(FAR const char *src,
              FAR unsigned char *target, size_t targsize);
 
+/* dn resolution */
+
+int dn_comp(FAR const char *src, FAR unsigned char *dst, int space,
+            FAR unsigned char **dnptrs, FAR unsigned char **lastdnptr);
+
+int dn_expand(FAR const unsigned char *base, FAR const unsigned char *end,
+              FAR const unsigned char *src, FAR char *dest, int space);
+
 #if defined(__cplusplus)
 }
 #endif

libs/libc/netdb/Make.defs

@@ -29,7 +29,7 @@ CSRCS += lib_gethostbyaddr.c lib_gethostbyaddrr.c
 CSRCS += lib_getservbyname.c lib_getservbynamer.c
 CSRCS += lib_getservbyport.c lib_getservbyportr.c
 CSRCS += lib_gaistrerror.c lib_freeaddrinfo.c lib_getaddrinfo.c
-CSRCS += lib_getnameinfo.c lib_rexec.c
+CSRCS += lib_getnameinfo.c lib_rexec.c lib_dn.c
 
 # Add host file support
 

libs/libc/netdb/lib_dn.c

@@ -0,0 +1,314 @@
+/****************************************************************************
+ * libs/libc/netdb/lib_dn.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <string.h>
+#include <resolv.h>
+
+/* RFC 1035 message compression */
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/* label start offsets of a compressed domain name s */
+
+static int getoffs(FAR short *offs, FAR const unsigned char *base,
+                   FAR const unsigned char *s)
+{
+  int i = 0;
+
+  for (; ; )
+    {
+      while ((*s & 0xc0) != 0)
+        {
+          if ((*s & 0xc0) != 0xc0)
+            {
+              return 0;
+            }
+
+          s = base + ((s[0] & 0x3f) << 8 | s[1]);
+        }
+
+      if (*s == 0)
+        {
+          return i;
+        }
+
+      if (s - base >= 0x4000)
+        {
+          return 0;
+        }
+
+      offs[i++] = s - base;
+      s += *s + 1;
+    }
+}
+
+/* label lengths of an ascii domain name s */
+
+static int getlens(FAR unsigned char *lens, FAR const char *s, int l)
+{
+  int i = 0;
+  int j = 0;
+  int k = 0;
+
+  for (; ; )
+    {
+      for (; j < l && s[j] != '.'; j++);
+      if (j - k - 1 > 62)
+        {
+          return 0;
+        }
+
+      lens[i++] = j - k;
+      if (j == l)
+        {
+          return i;
+        }
+
+      k = ++j;
+    }
+}
+
+/* longest suffix match of an ascii domain with a compressed domain name dn */
+
+static int match(FAR int *offset, FAR const unsigned char *base,
+                 FAR const unsigned char *dn, FAR const char *end,
+                 FAR const unsigned char *lens, int nlen)
+{
+  int l;
+  int o;
+  int m = 0;
+  short offs[128];
+  int noff = getoffs(offs, base, dn);
+
+  if (noff == 0)
+    {
+      return 0;
+    }
+
+  for (; ; )
+    {
+      l = lens[--nlen];
+      o = offs[--noff];
+      end -= l;
+      if (l != base[o] || memcmp(base + o + 1, end, l) != 0)
+        {
+          return m;
+        }
+
+      *offset = o;
+      m += l;
+      if (nlen > 0)
+        {
+          m++;
+        }
+
+      if (nlen == 0 || noff == 0)
+        {
+          return m;
+        }
+
+      end--;
+    }
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+int dn_comp(FAR const char *src, FAR unsigned char *dst, int space,
+            FAR unsigned char **dnptrs, FAR unsigned char **lastdnptr)
+{
+  int i;
+  int j;
+  int n;
+  int m = 0;
+  int offset = 0;
+  int bestlen = 0;
+  int bestoff = 0;
+  unsigned char lens[127];
+  FAR unsigned char **p = dnptrs;
+  FAR const char *end;
+  size_t l = strnlen(src, 255);
+
+  if (l > 0 && src[l - 1] == '.')
+    {
+      l--;
+    }
+
+  if (l > 253 || space <= 0)
+    {
+      return -1;
+    }
+
+  if (l == 0)
+    {
+      *dst = 0;
+      return 1;
+    }
+
+  end = src + l;
+  n = getlens(lens, src, l);
+  if (n == 0)
+    {
+      return -1;
+    }
+
+  if (dnptrs != NULL && *dnptrs != NULL)
+    {
+      for (p = dnptrs + 1 ; *p != NULL; p++)
+        {
+          m = match(&offset, *dnptrs, *p, end, lens, n);
+          if (m > bestlen)
+            {
+              bestlen = m;
+              bestoff = offset;
+              if (m == l)
+                {
+                  break;
+                }
+            }
+        }
+    }
+
+  /* encode unmatched part */
+
+  if (space < l - bestlen + 2 + (bestlen - 1 < l - 1))
+    {
+      return -1;
+    }
+
+  memcpy(dst + 1, src, l - bestlen);
+  for (i = j = 0; i < l - bestlen; i += lens[j++] + 1)
+    {
+      dst[i] = lens[j];
+    }
+
+  /* add tail */
+
+  if (bestlen > 0)
+    {
+      dst[i++] = 0xc0 | bestoff >> 8;
+      dst[i++] = bestoff;
+    }
+  else
+    {
+      dst[i++] = 0;
+    }
+
+  /* save dst pointer */
+
+  if (i > 2 && lastdnptr != NULL && dnptrs != NULL && *dnptrs != NULL)
+    {
+      while (*p != NULL)
+        {
+          p++;
+        }
+
+      if (p + 1 < lastdnptr)
+        {
+          *p++ = dst;
+          *p = 0;
+        }
+    }
+
+  return i;
+}
+
+int dn_expand(FAR const unsigned char *base, FAR const unsigned char *end,
+              FAR const unsigned char *src, FAR char *dest, int space)
+{
+  FAR const unsigned char *p = src;
+  FAR char *dend;
+  FAR char *dbegin = dest;
+  int len = -1;
+  int i;
+  int j;
+
+  if (p == end || space <= 0)
+    {
+      return -1;
+    }
+
+  dend = dest + (space > 254 ? 254 : space);
+
+  /* detect reference loop using an iteration counter */
+
+  for (i = 0; i < end - base; i += 2)
+    {
+      /* loop invariants: p<end, dest<dend */
+
+      if ((*p & 0xc0) != 0)
+        {
+          if (p + 1 == end)
+            {
+              return -1;
+            }
+
+          j = ((p[0] & 0x3f) << 8) | p[1];
+          if (len < 0)
+            {
+              len = p + 2 - src;
+            }
+
+          if (j >= end - base)
+            {
+              return -1;
+            }
+
+          p = base + j;
+        }
+      else if (*p)
+        {
+          if (dest != dbegin)
+            {
+              *dest++ = '.';
+            }
+
+          j = *p++;
+          if (j >= end - p || j >= dend - dest)
+            {
+              return -1;
+            }
+
+          while (j--)
+            {
+              *dest++ = *p++;
+            }
+        }
+      else
+        {
+          *dest = 0;
+          if (len < 0)
+            {
+              len = p + 1 - src;
+            }
+
+          return len;
+        }
+    }
+
+  return -1;
+}