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71e016d80

Denys Vlasenko

2018-04-14

SUCCESS Duration: 146s

Subject

nslookup: shrink send_queries()

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Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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Commit Diff GitHub →

networking/nslookup.c +123 -118

networking/nslookup.c+123 -118

@@ -263,10 +263,10 @@ struct ns {

	struct query {
	const char *name;
-	size_t qlen, rlen;
+	unsigned qlen, rlen;
+	unsigned latency;
+	uint8_t rcode;
	unsigned char query[512], reply[512];
-	unsigned long latency;
-	int rcode;
	};

	static const struct {
@@ -288,23 +288,22 @@ static const struct {
	};

	static const char *const rcodes[] = {
-	"NOERROR",
-	"FORMERR",
-	"SERVFAIL",
-	"NXDOMAIN",
-	"NOTIMP",
-	"REFUSED",
-	"YXDOMAIN",
-	"YXRRSET",
-	"NXRRSET",
-	"NOTAUTH",
-	"NOTZONE",
-	"RESERVED11",
-	"RESERVED12",
-	"RESERVED13",
-	"RESERVED14",
-	"RESERVED15",
-	"BADVERS"
+	"NOERROR", // 0
+	"FORMERR", // 1
+	"SERVFAIL", // 2
+	"NXDOMAIN", // 3
+	"NOTIMP", // 4
+	"REFUSED", // 5
+	"YXDOMAIN", // 6
+	"YXRRSET", // 7
+	"NXRRSET", // 8
+	"NOTAUTH", // 9
+	"NOTZONE", // 10
+	"11", // 11 not assigned
+	"12", // 12 not assigned
+	"13", // 13 not assigned
+	"14", // 14 not assigned
+	"15", // 15 not assigned
	};

	#if ENABLE_FEATURE_IPV6
@@ -518,131 +517,136 @@ static char make_ptr(char resbuf[80], const char addrstr)

	/*
	* Function logic borrowed & modified from musl libc, res_msend.c
+	* n_queries is always > 0.
	*/
-	static int send_queries(struct ns ns, struct query queries, int n_queries)
+	static int send_queries(struct ns ns, struct query query, int n_queries)
	{
+	len_and_sockaddr *local_lsa;
	struct pollfd pfd;
	int servfail_retry = 0;
	int n_replies = 0;
-	int next_query = 0;
+	int save_idx = 0;
	unsigned retry_interval;
	unsigned timeout = G.default_timeout * 1000;
-	unsigned t0, t1, t2;
+	unsigned tstart, tsent, tcur;

-	pfd.fd = -1;
	pfd.events = POLLIN;
+	pfd.fd = xsocket_type(&local_lsa, ns->lsa->u.sa.sa_family, SOCK_DGRAM);
+	/*
+	* local_lsa has "null" address and port 0 now.
+	* bind() ensures we have a particular port selected by kernel
+	* and remembered in fd, thus later recv(fd)
+	* receives only packets sent to this port.
+	*/
+	xbind(pfd.fd, &local_lsa->u.sa, local_lsa->len);
+	free(local_lsa);
+	/* Make read/writes know the destination */
+	xconnect(pfd.fd, &ns->lsa->u.sa, ns->lsa->len);
+	ndelay_on(pfd.fd);

	retry_interval = timeout / G.default_retry;
-	t0 = t2 = monotonic_ms();
-	t1 = t2 - retry_interval;
+	tstart = tcur = monotonic_ms();
+	goto send;
+
+	while (tcur - tstart < timeout) {
+	int qn;
+	int recvlen;

-	for (; t2 - t0 < timeout; t2 = monotonic_ms()) {
-	if (t2 - t1 >= retry_interval) {
-	int qn;
+	if (tcur - tsent >= retry_interval) {
+	send:
	for (qn = 0; qn < n_queries; qn++) {
-	if (queries[qn].rlen)
+	if (query[qn].rlen)
	continue;
-	if (pfd.fd < 0) {
-	len_and_sockaddr *local_lsa;
-	pfd.fd = xsocket_type(&local_lsa, ns->lsa->u.sa.sa_family, SOCK_DGRAM);
-	/*
-	* local_lsa has "null" address and port 0 now.
-	* bind() ensures we have a particular port selected by kernel
-	* and remembered in fd, thus later recv(fd)
-	* receives only packets sent to this port.
-	*/
-	xbind(pfd.fd, &local_lsa->u.sa, local_lsa->len);
-	free(local_lsa);
-	/* Make read/writes know the destination */
-	xconnect(pfd.fd, &ns->lsa->u.sa, ns->lsa->len);
-	ndelay_on(pfd.fd);
-	}
-	if (write(pfd.fd, queries[qn].query, queries[qn].qlen) < 0) {
+	if (write(pfd.fd, query[qn].query, query[qn].qlen) < 0) {
	bb_perror_msg("write to '%s'", ns->name);
-	close(pfd.fd);
-	return -1; /* "no go, try next server" */
+	n_replies = -1; /* "no go, try next server" */
+	goto ret;
	}
+	dbg("query %u sent\n", qn);
	}
-
-	t1 = t2;
+	tsent = tcur;
	servfail_retry = 2 * n_queries;
	}
-	poll_more:
-	/* Wait for a response, or until time to retry */
-	if (poll(&pfd, 1, t1 + retry_interval - t2) <= 0)
-	continue;
-
-	while (1) {
-	int qn;
-	int recvlen;
-
-	recvlen = read(pfd.fd,
-	queries[next_query].reply,
-	sizeof(queries[next_query].reply)
-	);

-	/* read error */
-	if (recvlen < 0)
-	break;
-
-	/* Ignore non-identifiable packets */
-	if (recvlen < 4)
-	goto poll_more;
-
-	/* Find which query this answer goes with, if any */
-	for (qn = next_query; qn < n_queries; qn++)
-	if (memcmp(queries[next_query].reply, queries[qn].query, 2) == 0)
-	break;
-
-	if (qn >= n_queries \|\| queries[qn].rlen)
-	goto poll_more;
+	/* Wait for a response, or until time to retry */
+	if (poll(&pfd, 1, retry_interval - (tcur - tsent)) <= 0)
+	goto next;

-	queries[qn].rcode = queries[next_query].reply[3] & 15;
-	queries[qn].latency = monotonic_ms() - t0;
+	recvlen = read(pfd.fd, query[save_idx].reply, sizeof(query[0].reply));

-	ns->replies++;
+	/* Error/non-identifiable packet */
+	if (recvlen < 4) {
+	dbg("read is too short:%d\n", recvlen);
+	goto next;
+	}

-	/* Only accept positive or negative responses;
-	* retry immediately on server failure, and ignore
-	* all other codes such as refusal. */
-	switch (queries[qn].rcode) {
-	case 0:
-	case 3:
+	/* Find which query this answer goes with, if any */
+	qn = save_idx;
+	for (;;) {
+	if (memcmp(query[save_idx].reply, query[qn].query, 2) == 0) {
+	dbg("response matches query %u\n", qn);
	break;
-
-	case 2:
-	if (servfail_retry && servfail_retry--) {
-	ns->failures++;
-	write(pfd.fd, queries[qn].query, queries[qn].qlen);
-	}
-	/* fall through */
-
-	default:
-	continue;
	}
+	if (++qn >= n_queries) {
+	dbg("response does not match any query\n");
+	goto next;
+	}
+	}

-	/* Store answer */
-	n_replies++;
+	if (query[qn].rlen) {
+	dbg("dropped duplicate response to query %u\n", qn);
+	goto next;
+	}

-	queries[qn].rlen = recvlen;
+	ns->replies++;

-	if (qn == next_query) {
-	while (next_query < n_queries) {
-	if (!queries[next_query].rlen)
-	break;
-	next_query++;
-	}
-	} else {
-	memcpy(queries[qn].reply, queries[next_query].reply, recvlen);
+	query[qn].rcode = query[save_idx].reply[3] & 15;
+	dbg("query %u rcode:%s\n", qn, rcodes[query[qn].rcode]);
+
+	/* Only accept positive or negative responses;
+	* retry immediately on server failure, and ignore
+	* all other codes such as refusal.
+	*/
+	switch (query[qn].rcode) {
+	case 0:
+	case 3:
+	break;
+	case 2:
+	if (servfail_retry) {
+	servfail_retry--;
+	ns->failures++;
+	write(pfd.fd, query[qn].query, query[qn].qlen);
+	dbg("query %u resent\n", qn);
	}
+	/* fall through */
+	default:
+	next:
+	tcur = monotonic_ms();
+	continue;
+	}

-	if (next_query >= n_queries)
-	goto ret;
+	/* Store answer */
+	n_replies++;
+	query[qn].rlen = recvlen;
+	tcur = monotonic_ms();
+	query[qn].latency = tcur - tstart;
+	if (qn != save_idx) {
+	/* "wrong" receive buffer, move to correct one */
+	memcpy(query[qn].reply, query[save_idx].reply, recvlen);
+	continue;
	}
-	}
+	/* query[0..save_idx] have replies, move to next one, if exists */
+	for (;;) {
+	save_idx++;
+	if (save_idx >= n_queries)
+	goto ret; /* all are full: we have all results */
+	if (!query[save_idx].rlen)
+	break; /* this one is empty */
+	}
+	} /* while() */
+
	ret:
-	if (pfd.fd >= 0)
-	close(pfd.fd);
+	close(pfd.fd);

	return n_replies;
	}
@@ -791,12 +795,13 @@ int nslookup_main(int argc UNUSED_PARAM, char **argv)
	n_queries = 0;
	queries = NULL;
	do {
-	/* No explicit type given, guess query type.
-	* If we can convert the domain argument into a ptr (means that
-	* inet_pton() could read it) we assume a PTR request, else
-	* we issue A+AAAA queries and switch to an output format
-	* mimicking the one of the traditional nslookup applet. */
	if (types == 0) {
+	/* No explicit type given, guess query type.
+	* If we can convert the domain argument into a ptr (means that
+	* inet_pton() could read it) we assume a PTR request, else
+	* we issue A+AAAA queries and switch to an output format
+	* mimicking the one of the traditional nslookup applet.
+	*/
	char *ptr;
	char buf80[80];