4468c569f
Martin Lewis
2020-07-12
Subject
domain_codec: optimize dname_dec and convert_dname
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networking/udhcp/domain_codec.c+79 -78
| @@ -10,10 +10,14 @@ | |
| # define _GNU_SOURCE | |
| # define FAST_FUNC /* nothing */ | |
| # define xmalloc malloc | |
| + | # define xzalloc(s) calloc(s, 1) |
| + | # define xstrdup strdup |
| + | # define xrealloc realloc |
| # include <stdlib.h> | |
| # include <stdint.h> | |
| # include <string.h> | |
| # include <stdio.h> | |
| + | # include <ctype.h> |
| #else | |
| # include "common.h" | |
| #endif | |
| @@ -26,86 +30,77 @@ | |
| /* 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. | |
| */ | |
| char* FAST_FUNC dname_dec(const uint8_t *cstr, int clen, const char *pre) | |
| { | |
| - | char *ret = ret; /* for compiler */ |
| - | char *dst = NULL; |
| + | char *ret, *end; |
| + | unsigned len, crtpos, retpos, depth; |
| - | /* 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 (1) { |
| - | /* note: "return NULL" below are leak-safe since |
| - | * dst isn't allocated yet */ |
| + | crtpos = retpos = depth = 0; |
| + | len = strlen(pre); |
| + | end = ret = xstrdup(pre); |
| + | |
| + | /* Scan the string once, allocating new memory as needed */ |
| + | while (crtpos < clen) { |
| const uint8_t *c; | |
| - | unsigned crtpos, retpos, depth, len; |
| + | c = cstr + crtpos; |
| - | crtpos = retpos = depth = len = 0; |
| - | while (crtpos < clen) { |
| - | c = cstr + crtpos; |
| + | if ((*c & NS_CMPRSFLGS) == NS_CMPRSFLGS) { |
| + | /* pointer */ |
| + | 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) { |
| - | /* 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[0] & 0x3f) << 8) | c[1]; /* jump */ |
| - | } 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; |
| + | label_len = *c + 1; |
| + | len += label_len; |
| + | crtpos += label_len; |
| + | } else { |
| + | /* NUL: end of current domain name */ |
| + | if (retpos == 0) { |
| + | /* toplevel? keep going */ |
| + | crtpos++; |
| } else { | |
| - | /* NUL: 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 && len != 0) |
| - | /* \4host\3com\0\4host and we are at \0: |
| - | * \3com was converted to "com.", change dot to space. |
| - | */ |
| - | dst[len - 1] = ' '; |
| + | /* return to toplevel saved spot */ |
| + | crtpos = retpos; |
| + | retpos = depth = 0; |
| } | |
| - | 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 != 0) { |
| + | /* \4host\3com\0\4host and we are at \0: |
| + | * \3com was converted to "com.", change dot to space. |
| + | */ |
| + | ret[len - 1] = ' '; |
| } | |
| } | |
| - | if (!len) /* expanded string has 0 length? abort */ |
| - | return NULL; |
| - | |
| - | if (!dst) { /* first pass? */ |
| - | /* 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 (depth > NS_MAXDNSRCH /* too many jumps? abort, it's a loop */ |
| + | || len > NS_MAXDNAME * NS_MAXDNSRCH /* result too long? abort */ |
| + | ) { |
| + | goto error; |
| } | |
| } | |
| + | if (ret == end) { /* expanded string is empty? abort */ |
| + | error: |
| + | free(ret); |
| + | return NULL; |
| + | } |
| + | |
| + | *end = '\0'; |
| 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) | |
| { | |
| - | uint8_t c, *res, *lenptr, *dst; |
| - | int len; |
| + | uint8_t *res, *lenptr, *dst; |
| - | res = xmalloc(strlen(src) + 2); |
| + | res = xzalloc(strlen(src) + 2); |
| dst = lenptr = res; | |
| dst++; | |
| for (;;) { | |
| + | uint8_t c; |
| + | int len; |
| + | |
| c = (uint8_t)*src++; | |
| if (c == '.' || c == '\0') { /* end of label */ | |
| len = dst - lenptr - 1; | |
| - | /* label too long, too short, or two '.'s in a row? abort */ |
| - | if (len > NS_MAXLABEL || len == 0 || (c == '.' && *src == '.')) { |
| - | free(res); |
| - | *retlen = 0; |
| - | return NULL; |
| - | } |
| + | /* label too long, too short, or two '.'s in a row (len will be 0) */ |
| + | if (len > NS_MAXLABEL || len == 0) |
| + | goto error; |
| + | |
| *lenptr = len; | |
| if (c == '\0' || *src == '\0') /* "" or ".": end of src */ | |
| break; | |
| lenptr = dst++; | |
| continue; | |
| } | |
| - | if (c >= 'A' && c <= 'Z') /* uppercase? convert to lower */ |
| - | c += ('a' - 'A'); |
| - | *dst++ = c; |
| + | *dst++ = tolower(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); | |
| *retlen = 0; | |
| return NULL; | |
| } | |
| - | *dst++ = 0; |
| - | *retlen = dst - 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("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)) | |
| encoded = dname_enc(NULL, 0, "test.net", &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); | |
| encoded = DNAME_ENC("\4test\3net\0", "test.net", &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; | |
| } | |
| #endif | |