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 text data bss dec hex filename 981645 16915 1872 1000432 f43f0 busybox_old 981603 16915 1872 1000390 f43c6 busybox_unstripped Signed-off-by: Martin Lewis <[email protected]> --- networking/udhcp/domain_codec.c | 157 ++++++++++++++++++++-------------------- 1 file changed, 79 insertions(+), 78 deletions(-) diff --git a/networking/udhcp/domain_codec.c b/networking/udhcp/domain_codec.c index 752c0a863..092cd6661 100644 --- a/networking/udhcp/domain_codec.c +++ b/networking/udhcp/domain_codec.c @@ -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 @@ -31,81 +35,72 @@ */ 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[0] = '.'; - 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; + } else { + *dst++ = tolower(c); } - if (c >= 'A' && c <= 'Z') /* uppercase? convert to lower */ - 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); *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 -- 2.11.0 _______________________________________________ busybox mailing list [email protected] http://lists.busybox.net/mailman/listinfo/busybox
