source: azure_iot_hub/trunk/musl-1.1.18/src/network/ns_parse.c@ 388

#define _BSD_SOURCE
#include <errno.h>
#include <stddef.h>
#include <resolv.h>
#include <arpa/nameser.h>

const struct _ns_flagdata _ns_flagdata[16] = {
        { 0x8000, 15 },
        { 0x7800, 11 },
        { 0x0400, 10 },
        { 0x0200, 9 },
        { 0x0100, 8 },
        { 0x0080, 7 },
        { 0x0040, 6 },
        { 0x0020, 5 },
        { 0x0010, 4 },
        { 0x000f, 0 },
        { 0x0000, 0 },
        { 0x0000, 0 },
        { 0x0000, 0 },
        { 0x0000, 0 },
        { 0x0000, 0 },
        { 0x0000, 0 },
};

unsigned ns_get16(const unsigned char *cp)
{
        return cp[0]<<8 | cp[1];
}

unsigned long ns_get32(const unsigned char *cp)
{
        return (unsigned)cp[0]<<24 | cp[1]<<16 | cp[2]<<8 | cp[3];
}

void ns_put16(unsigned s, unsigned char *cp)
{
        *cp++ = s>>8;
        *cp++ = s;
}

void ns_put32(unsigned long l, unsigned char *cp)
{
        *cp++ = l>>24;
        *cp++ = l>>16;
        *cp++ = l>>8;
        *cp++ = l;
}

int ns_initparse(const unsigned char *msg, int msglen, ns_msg *handle)
{
        int i, r;

        handle->_msg = msg;
        handle->_eom = msg + msglen;
        if (msglen < (2 + ns_s_max) * NS_INT16SZ) goto bad;
        NS_GET16(handle->_id, msg);
        NS_GET16(handle->_flags, msg);
        for (i = 0; i < ns_s_max; i++) NS_GET16(handle->_counts[i], msg);
        for (i = 0; i < ns_s_max; i++) {
                if (handle->_counts[i]) {
                        handle->_sections[i] = msg;
                        r = ns_skiprr(msg, handle->_eom, i, handle->_counts[i]);
                        if (r < 0) return -1;
                        msg += r;
                } else {
                        handle->_sections[i] = NULL;
                }
        }
        if (msg != handle->_eom) goto bad;
        handle->_sect = ns_s_max;
        handle->_rrnum = -1;
        handle->_msg_ptr = NULL;
        return 0;
bad:
        errno = EMSGSIZE;
        return -1;
}

int ns_skiprr(const unsigned char *ptr, const unsigned char *eom, ns_sect section, int count)
{
        const unsigned char *p = ptr;
        int r;

        while (count--) {
                r = dn_skipname(p, eom);
                if (r < 0) goto bad;
                if (r + 2 * NS_INT16SZ > eom - p) goto bad;
                p += r + 2 * NS_INT16SZ;
                if (section != ns_s_qd) {
                        if (NS_INT32SZ + NS_INT16SZ > eom - p) goto bad;
                        p += NS_INT32SZ;
                        NS_GET16(r, p);
                        if (r > eom - p) goto bad;
                        p += r;
                }
        }
        return p - ptr;
bad:
        errno = EMSGSIZE;
        return -1;
}

int ns_parserr(ns_msg *handle, ns_sect section, int rrnum, ns_rr *rr)
{
        int r;

        if (section < 0 || section >= ns_s_max) goto bad;
        if (section != handle->_sect) {
                handle->_sect = section;
                handle->_rrnum = 0;
                handle->_msg_ptr = handle->_sections[section];
        }
        if (rrnum == -1) rrnum = handle->_rrnum;
        if (rrnum < 0 || rrnum >= handle->_counts[section]) goto bad;
        if (rrnum < handle->_rrnum) {
                handle->_rrnum = 0;
                handle->_msg_ptr = handle->_sections[section];
        }
        if (rrnum > handle->_rrnum) {
                r = ns_skiprr(handle->_msg_ptr, handle->_eom, section, rrnum - handle->_rrnum);
                if (r < 0) return -1;
                handle->_msg_ptr += r;
                handle->_rrnum = rrnum;
        }
        r = ns_name_uncompress(handle->_msg, handle->_eom, handle->_msg_ptr, rr->name, NS_MAXDNAME);
        if (r < 0) return -1;
        handle->_msg_ptr += r;
        if (2 * NS_INT16SZ > handle->_eom - handle->_msg_ptr) goto size;
        NS_GET16(rr->type, handle->_msg_ptr);
        NS_GET16(rr->rr_class, handle->_msg_ptr);
        if (section != ns_s_qd) {
                if (NS_INT32SZ + NS_INT16SZ > handle->_eom - handle->_msg_ptr) goto size;
                NS_GET32(rr->ttl, handle->_msg_ptr);
                NS_GET16(rr->rdlength, handle->_msg_ptr);
                if (rr->rdlength > handle->_eom - handle->_msg_ptr) goto size;
                rr->rdata = handle->_msg_ptr;
                handle->_msg_ptr += rr->rdlength;
        } else {
                rr->ttl = 0;
                rr->rdlength = 0;
                rr->rdata = NULL;
        }
        handle->_rrnum++;
        if (handle->_rrnum > handle->_counts[section]) {
                handle->_sect = section + 1;
                if (handle->_sect == ns_s_max) {
                        handle->_rrnum = -1;
                        handle->_msg_ptr = NULL;
                } else {
                        handle->_rrnum = 0;
                }
        }
        return 0;
bad:
        errno = ENODEV;
        return -1;
size:
        errno = EMSGSIZE;
        return -1;
}

int ns_name_uncompress(const unsigned char *msg, const unsigned char *eom,
                       const unsigned char *src, char *dst, size_t dstsiz)
{
        int r;
        r = dn_expand(msg, eom, src, dst, dstsiz);
        if (r < 0) errno = EMSGSIZE;
        return r;
}