56 lines
1.4 KiB
C
Executable file
56 lines
1.4 KiB
C
Executable file
/* dhcp_gettag() Author: Kees J. Bot
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* 1 Dec 2000
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*/
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#define nil ((void*)0)
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#include <stddef.h>
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#include <string.h>
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#include <sys/types.h>
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#include <net/hton.h>
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#include <net/gen/in.h>
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#include <net/gen/dhcp.h>
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#define arraysize(a) (sizeof(a) / sizeof((a)[0]))
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int dhcp_gettag(dhcp_t *dp, int searchtag, u8_t **pdata, size_t *plen)
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{
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/* Find a tag in the options field, or possibly in the file or sname
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* fields. Return true iff found, and return the data and/or length if
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* their pointers are non-null.
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*/
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u8_t *p;
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u8_t *optfield[3];
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size_t optlen[3];
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int i, tag, len;
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/* The DHCP magic number must be correct, or no tags. */
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if (dp->magic != DHCP_MAGIC) return 0;
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optfield[0]= dp->options;
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optlen[0]= arraysize(dp->options);
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optfield[1]= dp->file;
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optlen[1]= 0; /* Unknown if used for options yet. */
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optfield[2]= dp->sname;
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optlen[2]= 0;
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for (i= 0; i < 3; i++) {
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p= optfield[i];
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while (p < optfield[i] + optlen[i]) {
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tag= *p++;
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if (tag == 255) break;
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len= tag == 0 ? 0 : *p++;
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if (tag == searchtag) {
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if (pdata != nil) *pdata= p;
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if (plen != nil) *plen= len;
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return 1;
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}
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if (tag == DHCP_TAG_OVERLOAD) {
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/* There are also options in the file or sname field. */
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if (*p & 1) optlen[1]= arraysize(dp->file);
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if (*p & 2) optlen[1]= arraysize(dp->sname);
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}
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p += len;
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}
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}
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return 0;
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}
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