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Make minor improvements

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This commit is contained in:
Justine Tunney 2021-05-15 21:53:26 -07:00
parent 221817e537
commit 4864565198
41 changed files with 394 additions and 367 deletions
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112
libc/dns/resolvedns.c
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@ -38,7 +38,7 @@
/**
* Queries Domain Name System for address associated with name.
*
* @param resolvconf can be getresolvconf()
* @param resolvconf can be GetResolvConf()
* @param af can be AF_INET, AF_UNSPEC
* @param name can be a local or fully-qualified hostname
* @param addr should point to a struct sockaddr_in; if this function
@ -47,65 +47,62 @@
* @return number of matches found, or -1 w/ errno
* @error EAFNOSUPPORT. ENETDOWN, ENAMETOOLONG, EBADMSG
*/
int resolvedns(const struct ResolvConf *resolvconf, int af, const char *name,
int ResolveDns(const struct ResolvConf *resolvconf, int af, const char *name,
struct sockaddr *addr, uint32_t addrsize) {
size_t msgsize;
int res, fd, rc, rc2;
struct sockaddr_in *addr4;
struct DnsQuestion question;
int rc, fd, n;
struct DnsQuestion q;
struct DnsHeader h, h2;
struct sockaddr_in *a4;
uint8_t *p, *pe, msg[512];
uint16_t rtype, rclass, rdlength;
uint8_t *p, *pe, *outmsg, *inmsg;
struct DnsHeader header, response;
if (af != AF_INET && af != AF_UNSPEC) return eafnosupport();
if (!resolvconf->nameservers.i) return 0;
memset(&header, 0, sizeof(header));
header.id = rand32();
header.bf1 = 1; /* recursion desired */
header.qdcount = 1;
question.qname = name;
question.qtype = DNS_TYPE_A;
question.qclass = DNS_CLASS_IN;
res = -1;
if ((outmsg = malloc(kMsgMax)) && (inmsg = malloc(kMsgMax)) &&
(rc = serializednsheader(outmsg, kMsgMax, header)) != -1 &&
(rc2 = serializednsquestion(outmsg + rc, kMsgMax - rc, question)) != -1) {
msgsize = rc + rc2;
if ((fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) != -1 &&
sendto(fd, outmsg, msgsize, 0, (void *)&resolvconf->nameservers.p[0],
sizeof(resolvconf->nameservers.p[0])) == msgsize) {
if ((rc = recv(fd, inmsg, kMsgMax, 0)) != -1 &&
(rc2 = deserializednsheader(&response, inmsg, rc)) != -1 &&
response.id == header.id) {
res = 0;
if (response.ancount) {
p = inmsg + rc2;
pe = inmsg + rc;
while (p < pe && response.qdcount) {
p += strnlen((char *)p, pe - p) + 1 + 4;
response.qdcount--;
memset(&h, 0, sizeof(h));
rc = ebadmsg();
h.id = rand32();
h.bf1 = 1; /* recursion desired */
h.qdcount = 1;
q.qname = name;
q.qtype = DNS_TYPE_A;
q.qclass = DNS_CLASS_IN;
memset(msg, 0, sizeof(msg));
SerializeDnsHeader(msg, &h);
if ((n = SerializeDnsQuestion(msg + 12, 500, &q)) == -1) return -1;
if ((fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) return -1;
if (sendto(fd, msg, 12 + n, 0, resolvconf->nameservers.p,
sizeof(*resolvconf->nameservers.p)) == 12 + n &&
(n = read(fd, msg, 512)) >= 12) {
DeserializeDnsHeader(&h2, msg);
if (h2.id == h.id) {
rc = 0;
if (h2.ancount) {
p = msg + 12;
pe = msg + n;
while (p < pe && h2.qdcount) {
p += strnlen((char *)p, pe - p) + 1 + 4;
h2.qdcount--;
}
if (p + 1 < pe) {
if ((p[0] & 0b11000000) == 0b11000000) { /* name pointer */
p += 2;
} else {
p += strnlen((char *)p, pe - p) + 1;
}
if (p + 1 < pe) {
if ((p[0] & 0b11000000) == 0b11000000) { /* name pointer */
p += 2;
} else {
p += strnlen((char *)p, pe - p) + 1;
}
if (p + 2 + 2 + 4 + 2 < pe) {
rtype = READ16BE(p), p += 2;
rclass = READ16BE(p), p += 2;
/* ttl */ p += 4;
rdlength = READ16BE(p), p += 2;
if (p + rdlength <= pe && rdlength == 4 &&
(rtype == DNS_TYPE_A && rclass == DNS_CLASS_IN)) {
res = 1;
if (addrsize) {
if (addrsize >= kMinSockaddr4Size) {
addr4 = (struct sockaddr_in *)addr;
addr4->sin_family = AF_INET;
memcpy(&addr4->sin_addr.s_addr, p, 4);
} else {
res = einval();
}
if (p + 2 + 2 + 4 + 2 < pe) {
rtype = READ16BE(p), p += 2;
rclass = READ16BE(p), p += 2;
/* ttl */ p += 4;
rdlength = READ16BE(p), p += 2;
if (p + rdlength <= pe && rdlength == 4 &&
(rtype == DNS_TYPE_A && rclass == DNS_CLASS_IN)) {
rc = 1;
if (addrsize) {
if (addrsize >= kMinSockaddr4Size) {
a4 = (struct sockaddr_in *)addr;
a4->sin_family = AF_INET;
memcpy(&a4->sin_addr.s_addr, p, 4);
} else {
rc = einval();
}
}
}
@ -113,8 +110,7 @@ int resolvedns(const struct ResolvConf *resolvconf, int af, const char *name,
}
}
}
res |= close(fd);
}
free(outmsg);
return res;
close(fd);
return rc;
}