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domain_codec: optimize dname_dec and convert_dname

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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 2020-07-09 14:47:05 -05:00 committed by Denys Vlasenko
parent 051665ef69
commit 4468c569f7
1 changed files with 79 additions and 78 deletions
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157
networking/udhcp/domain_codec.c
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@ -10,10 +10,14 @@
# define _GNU_SOURCE # define _GNU_SOURCE
# define FAST_FUNC /* nothing */ # define FAST_FUNC /* nothing */
# define xmalloc malloc # define xmalloc malloc
# define xzalloc(s) calloc(s, 1)
# define xstrdup strdup
# define xrealloc realloc
# include <stdlib.h> # include <stdlib.h>
# include <stdint.h> # include <stdint.h>
# include <string.h> # include <string.h>
# include <stdio.h> # include <stdio.h>
# include <ctype.h>
#else #else
# include "common.h" # include "common.h"
#endif #endif
@ -26,86 +30,77 @@
/* Expand a RFC1035-compressed list of domain names "cstr", of length "clen"; /* Expand a RFC1035-compressed list of domain names "cstr", of length "clen";
* returns a newly allocated string containing the space-separated domains, * return a newly allocated string containing the space-separated domains,
* prefixed with the contents of string pre, or NULL if an error occurs. * prefixed with the contents of string pre, or NULL if an error occurs.
*/ */
char* FAST_FUNC dname_dec(const uint8_t *cstr, int clen, const char *pre) char* FAST_FUNC dname_dec(const uint8_t *cstr, int clen, const char *pre)
{ {
char *ret = ret; /* for compiler */ char *ret, *end;
char *dst = NULL; unsigned len, crtpos, retpos, depth;
/* We make two passes over the cstr string. First, we compute crtpos = retpos = depth = 0;
* how long the resulting string would be. Then we allocate a len = strlen(pre);
* new buffer of the required length, and fill it in with the end = ret = xstrdup(pre);
* expanded content. The advantage of this approach is not
* having to deal with requiring callers to supply their own /* Scan the string once, allocating new memory as needed */
* buffer, then having to check if it's sufficiently large, etc. while (crtpos < clen) {
*/
while (1) {
/* note: "return NULL" below are leak-safe since
* dst isn't allocated yet */
const uint8_t *c; const uint8_t *c;
unsigned crtpos, retpos, depth, len; c = cstr + crtpos;
crtpos = retpos = depth = len = 0; if ((*c & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
while (crtpos < clen) { /* pointer */
c = cstr + crtpos; if (crtpos + 2 > clen) /* no offset to jump to? abort */
goto error;
if (retpos == 0) /* toplevel? save return spot */
retpos = crtpos + 2;
depth++;
crtpos = ((c[0] << 8) | c[1]) & 0x3fff; /* jump */
} else if (*c) {
unsigned label_len;
/* label */
if (crtpos + *c + 1 > clen) /* label too long? abort */
goto error;
ret = xrealloc(ret, len + *c + 1);
/* \3com ---> "com." */
end = (char *)mempcpy(ret + len, c + 1, *c);
*end = '.';
if ((*c & NS_CMPRSFLGS) == NS_CMPRSFLGS) { label_len = *c + 1;
/* pointer */ len += label_len;
if (crtpos + 2 > clen) /* no offset to jump to? abort */ crtpos += label_len;
return NULL; } else {
if (retpos == 0) /* toplevel? save return spot */ /* NUL: end of current domain name */
retpos = crtpos + 2; if (retpos == 0) {
depth++; /* toplevel? keep going */
crtpos = ((c[0] & 0x3f) << 8) | c[1]; /* jump */ crtpos++;
} else if (*c) {
/* label */
if (crtpos + *c + 1 > clen) /* label too long? abort */
return NULL;
if (dst)
/* \3com ---> "com." */
((char*)mempcpy(dst + len, c + 1, *c))[0] = '.';
len += *c + 1;
crtpos += *c + 1;
} else { } else {
/* NUL: end of current domain name */ /* return to toplevel saved spot */
if (retpos == 0) { crtpos = retpos;
/* toplevel? keep going */ retpos = depth = 0;
crtpos++;
} else {
/* return to toplevel saved spot */
crtpos = retpos;
retpos = depth = 0;
}
if (dst && len != 0)
/* \4host\3com\0\4host and we are at \0:
* \3com was converted to "com.", change dot to space.
*/
dst[len - 1] = ' ';
} }
if (depth > NS_MAXDNSRCH /* too many jumps? abort, it's a loop */ if (len != 0) {
|| len > NS_MAXDNAME * NS_MAXDNSRCH /* result too long? abort */ /* \4host\3com\0\4host and we are at \0:
) { * \3com was converted to "com.", change dot to space.
return NULL; */
ret[len - 1] = ' ';
} }
} }
if (!len) /* expanded string has 0 length? abort */ if (depth > NS_MAXDNSRCH /* too many jumps? abort, it's a loop */
return NULL; || len > NS_MAXDNAME * NS_MAXDNSRCH /* result too long? abort */
) {
if (!dst) { /* first pass? */ goto error;
/* allocate dst buffer and copy pre */
unsigned plen = strlen(pre);
ret = xmalloc(plen + len);
dst = stpcpy(ret, pre);
} else {
dst[len - 1] = '\0';
break;
} }
} }
if (ret == end) { /* expanded string is empty? abort */
error:
free(ret);
return NULL;
}
*end = '\0';
return ret; return ret;
} }
@ -115,42 +110,40 @@ char* FAST_FUNC dname_dec(const uint8_t *cstr, int clen, const char *pre)
*/ */
static uint8_t *convert_dname(const char *src, int *retlen) static uint8_t *convert_dname(const char *src, int *retlen)
{ {
uint8_t c, *res, *lenptr, *dst; uint8_t *res, *lenptr, *dst;
int len;
res = xmalloc(strlen(src) + 2); res = xzalloc(strlen(src) + 2);
dst = lenptr = res; dst = lenptr = res;
dst++; dst++;
for (;;) { for (;;) {
uint8_t c;
int len;
c = (uint8_t)*src++; c = (uint8_t)*src++;
if (c == '.' || c == '\0') { /* end of label */ if (c == '.' || c == '\0') { /* end of label */
len = dst - lenptr - 1; len = dst - lenptr - 1;
/* label too long, too short, or two '.'s in a row? abort */ /* label too long, too short, or two '.'s in a row (len will be 0) */
if (len > NS_MAXLABEL || len == 0 || (c == '.' && *src == '.')) { if (len > NS_MAXLABEL || len == 0)
free(res); goto error;
*retlen = 0;
return NULL;
}
*lenptr = len; *lenptr = len;
if (c == '\0' || *src == '\0') /* "" or ".": end of src */ if (c == '\0' || *src == '\0') /* "" or ".": end of src */
break; break;
lenptr = dst++; lenptr = dst++;
continue; continue;
} }
if (c >= 'A' && c <= 'Z') /* uppercase? convert to lower */ *dst++ = tolower(c);
c += ('a' - 'A');
*dst++ = c;
} }
if (dst - res >= NS_MAXCDNAME) { /* dname too long? abort */ *retlen = dst + 1 - res;
if (*retlen > NS_MAXCDNAME) { /* dname too long? abort */
error:
free(res); free(res);
*retlen = 0; *retlen = 0;
return NULL; return NULL;
} }
*dst++ = 0;
*retlen = dst - res;
return res; return res;
} }
@ -245,6 +238,7 @@ int main(int argc, char **argv)
printf("test4:'%s'\n", DNAME_DEC("\4host\3com\0\xC0\5", "")); printf("test4:'%s'\n", DNAME_DEC("\4host\3com\0\xC0\5", ""));
printf("test5:'%s'\n", DNAME_DEC("\4host\3com\0\xC0\5\1z\xC0\xA", "")); printf("test5:'%s'\n", DNAME_DEC("\4host\3com\0\xC0\5\1z\xC0\xA", ""));
#if 0
#define DNAME_ENC(cache,source,lenp) dname_enc((uint8_t*)(cache), sizeof(cache), (source), (lenp)) #define DNAME_ENC(cache,source,lenp) dname_enc((uint8_t*)(cache), sizeof(cache), (source), (lenp))
encoded = dname_enc(NULL, 0, "test.net", &len); encoded = dname_enc(NULL, 0, "test.net", &len);
printf("test6:'%s' len:%d\n", dname_dec(encoded, len, ""), len); printf("test6:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
@ -252,6 +246,13 @@ int main(int argc, char **argv)
printf("test7:'%s' len:%d\n", dname_dec(encoded, len, ""), len); printf("test7:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
encoded = DNAME_ENC("\4test\3net\0", "test.net", &len); encoded = DNAME_ENC("\4test\3net\0", "test.net", &len);
printf("test8:'%s' len:%d\n", dname_dec(encoded, len, ""), len); printf("test8:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
#endif
encoded = dname_enc("test.net", &len);
printf("test6:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
encoded = dname_enc("test.host.com", &len);
printf("test7:'%s' len:%d\n", dname_dec(encoded, len, ""), len);
return 0; return 0;
} }
#endif #endif