domain_codec: optimize dname_dec and convert_dname
dname_dec: now iterates over the packet only once. convert_dname: remove redundant checks and code shrink. While testing I've noticed that some of the tests didn't compile properly, so I fixed them. function old new delta dname_dec 286 267 -19 dname_enc 166 143 -23 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-42) Total: -42 bytes Signed-off-by: Martin Lewis <martin.lewis.x84@gmail.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Martin Lewis
Denys Vlasenko
parent
051665ef69
commit
4468c569f7
@ -10,10 +10,14 @@
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# define _GNU_SOURCE
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# define FAST_FUNC /* nothing */
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# define xmalloc malloc
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# define xzalloc(s) calloc(s, 1)
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# define xstrdup strdup
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# define xrealloc realloc
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# include <stdlib.h>
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# include <stdint.h>
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# include <string.h>
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# include <stdio.h>
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# include <ctype.h>
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#else
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# include "common.h"
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#endif
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@ -26,86 +30,77 @@
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/* Expand a RFC1035-compressed list of domain names "cstr", of length "clen";
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* returns a newly allocated string containing the space-separated domains,
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* return a newly allocated string containing the space-separated domains,
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* prefixed with the contents of string pre, or NULL if an error occurs.
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*/
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char* FAST_FUNC dname_dec(const uint8_t *cstr, int clen, const char *pre)
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{
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char *ret = ret; /* for compiler */
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char *dst = NULL;
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char *ret, *end;
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unsigned len, crtpos, retpos, depth;
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/* We make two passes over the cstr string. First, we compute
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* how long the resulting string would be. Then we allocate a
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* new buffer of the required length, and fill it in with the
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* expanded content. The advantage of this approach is not
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* having to deal with requiring callers to supply their own
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* buffer, then having to check if it's sufficiently large, etc.
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*/
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while (1) {
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/* note: "return NULL" below are leak-safe since
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* dst isn't allocated yet */
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crtpos = retpos = depth = 0;
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len = strlen(pre);
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end = ret = xstrdup(pre);
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/* Scan the string once, allocating new memory as needed */
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while (crtpos < clen) {
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const uint8_t *c;
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unsigned crtpos, retpos, depth, len;
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c = cstr + crtpos;
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crtpos = retpos = depth = len = 0;
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while (crtpos < clen) {
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c = cstr + crtpos;
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if ((*c & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
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/* pointer */
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if (crtpos + 2 > clen) /* no offset to jump to? abort */
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goto error;
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if (retpos == 0) /* toplevel? save return spot */
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retpos = crtpos + 2;
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depth++;
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crtpos = ((c[0] << 8) | c[1]) & 0x3fff; /* jump */
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} else if (*c) {
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unsigned label_len;
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/* label */
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if (crtpos + *c + 1 > clen) /* label too long? abort */
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goto error;
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ret = xrealloc(ret, len + *c + 1);
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/* \3com ---> "com." */
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end = (char *)mempcpy(ret + len, c + 1, *c);
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*end = '.';
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if ((*c & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
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/* pointer */
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if (crtpos + 2 > clen) /* no offset to jump to? abort */
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return NULL;
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if (retpos == 0) /* toplevel? save return spot */
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retpos = crtpos + 2;
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depth++;
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crtpos = ((c[0] & 0x3f) << 8) | c[1]; /* jump */
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} else if (*c) {
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/* label */
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if (crtpos + *c + 1 > clen) /* label too long? abort */
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return NULL;
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if (dst)
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/* \3com ---> "com." */
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((char*)mempcpy(dst + len, c + 1, *c))[0] = '.';
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len += *c + 1;
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crtpos += *c + 1;
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label_len = *c + 1;
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len += label_len;
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crtpos += label_len;
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} else {
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/* NUL: end of current domain name */
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if (retpos == 0) {
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/* toplevel? keep going */
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crtpos++;
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} else {
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/* NUL: end of current domain name */
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if (retpos == 0) {
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/* toplevel? keep going */
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crtpos++;
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} else {
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/* return to toplevel saved spot */
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crtpos = retpos;
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retpos = depth = 0;
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}
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if (dst && len != 0)
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/* \4host\3com\0\4host and we are at \0:
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* \3com was converted to "com.", change dot to space.
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*/
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dst[len - 1] = ' ';
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/* return to toplevel saved spot */
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crtpos = retpos;
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retpos = depth = 0;
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}
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if (depth > NS_MAXDNSRCH /* too many jumps? abort, it's a loop */
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|| len > NS_MAXDNAME * NS_MAXDNSRCH /* result too long? abort */
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) {
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return NULL;
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if (len != 0) {
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/* \4host\3com\0\4host and we are at \0:
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* \3com was converted to "com.", change dot to space.
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*/
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ret[len - 1] = ' ';
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}
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}
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if (!len) /* expanded string has 0 length? abort */
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return NULL;
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if (!dst) { /* first pass? */
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/* allocate dst buffer and copy pre */
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unsigned plen = strlen(pre);
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ret = xmalloc(plen + len);
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dst = stpcpy(ret, pre);
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} else {
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dst[len - 1] = '\0';
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break;
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if (depth > NS_MAXDNSRCH /* too many jumps? abort, it's a loop */
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|| len > NS_MAXDNAME * NS_MAXDNSRCH /* result too long? abort */
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) {
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goto error;
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}
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}
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if (ret == end) { /* expanded string is empty? abort */
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error:
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free(ret);
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return NULL;
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}
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*end = '\0';
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return ret;
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}
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@ -115,42 +110,40 @@ char* FAST_FUNC dname_dec(const uint8_t *cstr, int clen, const char *pre)
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*/
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static uint8_t *convert_dname(const char *src, int *retlen)
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{
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uint8_t c, *res, *lenptr, *dst;
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int len;
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uint8_t *res, *lenptr, *dst;
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res = xmalloc(strlen(src) + 2);
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res = xzalloc(strlen(src) + 2);
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dst = lenptr = res;
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dst++;
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for (;;) {
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uint8_t c;
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int len;
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c = (uint8_t)*src++;
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if (c == '.' || c == '\0') { /* end of label */
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len = dst - lenptr - 1;
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/* label too long, too short, or two '.'s in a row? abort */
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if (len > NS_MAXLABEL || len == 0 || (c == '.' && *src == '.')) {
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free(res);
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*retlen = 0;
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return NULL;
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}
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/* label too long, too short, or two '.'s in a row (len will be 0) */
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if (len > NS_MAXLABEL || len == 0)
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goto error;
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*lenptr = len;
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if (c == '\0' || *src == '\0') /* "" or ".": end of src */
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break;
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lenptr = dst++;
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continue;
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}
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if (c >= 'A' && c <= 'Z') /* uppercase? convert to lower */
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c += ('a' - 'A');
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*dst++ = c;
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*dst++ = tolower(c);
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}
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if (dst - res >= NS_MAXCDNAME) { /* dname too long? abort */
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*retlen = dst + 1 - res;
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if (*retlen > NS_MAXCDNAME) { /* dname too long? abort */
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error:
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free(res);
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*retlen = 0;
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return NULL;
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}
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*dst++ = 0;
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*retlen = dst - res;
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return res;
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}
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@ -245,6 +238,7 @@ int main(int argc, char **argv)
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printf("test4:'%s'\n", DNAME_DEC("\4host\3com\0\xC0\5", ""));
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printf("test5:'%s'\n", DNAME_DEC("\4host\3com\0\xC0\5\1z\xC0\xA", ""));
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#if 0
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#define DNAME_ENC(cache,source,lenp) dname_enc((uint8_t*)(cache), sizeof(cache), (source), (lenp))
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encoded = dname_enc(NULL, 0, "test.net", &len);
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printf("test6:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
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@ -252,6 +246,13 @@ int main(int argc, char **argv)
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printf("test7:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
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encoded = DNAME_ENC("\4test\3net\0", "test.net", &len);
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printf("test8:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
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#endif
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encoded = dname_enc("test.net", &len);
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printf("test6:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
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encoded = dname_enc("test.host.com", &len);
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printf("test7:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
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return 0;
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}
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#endif
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