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2cf75b3c8

Denys Vlasenko

2018-04-15

SUCCESS Duration: 144s

Subject

nslookup: process replies immediately, do not store them

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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

—

Build Log

(log yok)

Commit Diff GitHub →

networking/nslookup.c +110 -86

networking/nslookup.c+110 -86

@@ -264,9 +264,10 @@ struct ns {
	struct query {
	const char *name;
	unsigned qlen, rlen;
-	unsigned latency;
-	uint8_t rcode;
-	unsigned char query[512], reply[512];
+	// unsigned latency;
+	// uint8_t rcode;
+	unsigned char query[512];
+	// unsigned char reply[512];
	};

	static const struct {
@@ -325,9 +326,14 @@ struct globals {
	G.default_timeout = 5; \
	} while (0)

-	static int
-	parse_reply(const unsigned char *msg, size_t len)
+	enum {
+	OPT_stats = (1 << 4),
+	};
+
+	static int parse_reply(const unsigned char *msg, size_t len)
	{
+	HEADER *header;
+
	ns_msg handle;
	ns_rr rr;
	int i, n, rdlen;
@@ -335,14 +341,18 @@ parse_reply(const unsigned char *msg, size_t len)
	char astr[INET6_ADDRSTRLEN], dname[MAXDNAME];
	const unsigned char *cp;

+	header = (HEADER *)msg;
+	if (!header->aa)
+	printf("Non-authoritative answer:\n");
+
	if (ns_initparse(msg, len, &handle) != 0) {
-	//fprintf(stderr, "Unable to parse reply: %s\n", strerror(errno));
+	//printf("Unable to parse reply: %s\n", strerror(errno));
	return -1;
	}

	for (i = 0; i < ns_msg_count(handle, ns_s_an); i++) {
	if (ns_parserr(&handle, ns_s_an, i, &rr) != 0) {
-	//fprintf(stderr, "Unable to parse resource record: %s\n", strerror(errno));
+	//printf("Unable to parse resource record: %s\n", strerror(errno));
	return -1;
	}

@@ -387,7 +397,7 @@ parse_reply(const unsigned char *msg, size_t len)
	if (ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
	ns_rr_rdata(rr), dname, sizeof(dname)) < 0
	) {
-	//fprintf(stderr, "Unable to uncompress domain: %s\n", strerror(errno));
+	//printf("Unable to uncompress domain: %s\n", strerror(errno));
	return -1;
	}
	printf(format, ns_rr_name(rr), dname);
@@ -395,14 +405,14 @@ parse_reply(const unsigned char *msg, size_t len)

	case ns_t_mx:
	if (rdlen < 2) {
-	fprintf(stderr, "MX record too short\n");
+	printf("MX record too short\n");
	return -1;
	}
	n = ns_get16(ns_rr_rdata(rr));
	if (ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
	ns_rr_rdata(rr) + 2, dname, sizeof(dname)) < 0
	) {
-	//fprintf(stderr, "Cannot uncompress MX domain: %s\n", strerror(errno));
+	//printf("Cannot uncompress MX domain: %s\n", strerror(errno));
	return -1;
	}
	printf("%s\tmail exchanger = %d %s\n", ns_rr_name(rr), n, dname);
@@ -410,7 +420,7 @@ parse_reply(const unsigned char *msg, size_t len)

	case ns_t_txt:
	if (rdlen < 1) {
-	//fprintf(stderr, "TXT record too short\n");
+	//printf("TXT record too short\n");
	return -1;
	}
	n = (unsigned char )ns_rr_rdata(rr);
@@ -433,7 +443,7 @@ parse_reply(const unsigned char *msg, size_t len)
	n = ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
	cp, dname, sizeof(dname));
	if (n < 0) {
-	//fprintf(stderr, "Unable to uncompress domain: %s\n", strerror(errno));
+	//printf("Unable to uncompress domain: %s\n", strerror(errno));
	return -1;
	}

@@ -443,7 +453,7 @@ parse_reply(const unsigned char *msg, size_t len)
	n = ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle),
	cp, dname, sizeof(dname));
	if (n < 0) {
-	//fprintf(stderr, "Unable to uncompress domain: %s\n", strerror(errno));
+	//printf("Unable to uncompress domain: %s\n", strerror(errno));
	return -1;
	}

@@ -513,11 +523,13 @@ static char make_ptr(char resbuf[80], const char addrstr)
	*/
	static int send_queries(struct ns ns, struct query query, int n_queries)
	{
+	unsigned char reply[512];
+	uint8_t rcode;
	len_and_sockaddr *local_lsa;
	struct pollfd pfd;
	int servfail_retry = 0;
	int n_replies = 0;
-	int save_idx = 0;
+	// int save_idx = 0;
	unsigned retry_interval;
	unsigned timeout = G.default_timeout * 1000;
	unsigned tstart, tsent, tcur;
@@ -564,18 +576,34 @@ static int send_queries(struct ns ns, struct query query, int n_queries)
	if (poll(&pfd, 1, retry_interval - (tcur - tsent)) <= 0)
	goto next;

-	recvlen = read(pfd.fd, query[save_idx].reply, sizeof(query[0].reply));
+	recvlen = read(pfd.fd, reply, sizeof(reply));
+	if (recvlen < 0) {
+	bb_perror_msg("read");
+	next:
+	tcur = monotonic_ms();
+	continue;
+	}

-	/* Error/non-identifiable packet */
+	if (ns->replies++ == 0) {
+	printf("Server:\t\t%s\n", ns->name);
+	printf("Address:\t%s\n\n",
+	auto_string(xmalloc_sockaddr2dotted(&ns->lsa->u.sa))
+	);
+	/* In "Address", bind-utils-9.11.3 show port after a hash: "1.2.3.4#53" */
+	/* Should we do the same? */
+	}
+
+	/* Non-identifiable packet */
	if (recvlen < 4) {
	dbg("read is too short:%d\n", recvlen);
	goto next;
	}

	/* Find which query this answer goes with, if any */
-	qn = save_idx;
+	// qn = save_idx;
+	qn = 0;
	for (;;) {
-	if (memcmp(query[save_idx].reply, query[qn].query, 2) == 0) {
+	if (memcmp(reply, query[qn].query, 2) == 0) {
	dbg("response matches query %u\n", qn);
	break;
	}
@@ -590,38 +618,42 @@ static int send_queries(struct ns ns, struct query query, int n_queries)
	goto next;
	}

-	ns->replies++;
-
-	query[qn].rcode = query[save_idx].reply[3] & 15;
-	dbg("query %u rcode:%s\n", qn, rcodes[query[qn].rcode]);
+	rcode = reply[3] & 0x0f;
+	dbg("query %u rcode:%s\n", qn, rcodes[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:
+	/* Retry immediately on SERVFAIL */
+	if (rcode == 2) {
+	ns->failures++;
	if (servfail_retry) {
	servfail_retry--;
-	ns->failures++;
	write(pfd.fd, query[qn].query, query[qn].qlen);
	dbg("query %u resent\n", qn);
+	goto next;
	}
-	/* fall through */
-	default:
-	next:
-	tcur = monotonic_ms();
-	continue;
	}

-	/* Store answer */
-	n_replies++;
+	/* Process reply */
	query[qn].rlen = recvlen;
	tcur = monotonic_ms();
+	#if 1
+	if (option_mask32 & OPT_stats) {
+	printf("Query #%d completed in %ums:\n", qn, tcur - tstart);
+	}
+	if (rcode != 0) {
+	printf("** server can't find %s: %s\n",
+	query[qn].name, rcodes[rcode]);
+	} else {
+	if (parse_reply(reply, recvlen) < 0)
+	printf("*** Can't find %s: Parse error\n", query[qn].name);
+	}
+	bb_putchar('\n');
+	n_replies++;
+	if (n_replies >= n_queries)
+	goto ret;
+	#else
+	//used to store replies and process them later
	query[qn].latency = tcur - tstart;
+	n_replies++;
	if (qn != save_idx) {
	/* "wrong" receive buffer, move to correct one */
	memcpy(query[qn].reply, query[save_idx].reply, recvlen);
@@ -635,6 +667,7 @@ static int send_queries(struct ns ns, struct query query, int n_queries)
	if (!query[save_idx].rlen)
	break; /* this one is empty */
	}
+	#endif
	} /* while() */

	ret:
@@ -718,11 +751,9 @@ int nslookup_main(int argc UNUSED_PARAM, char **argv)
	llist_t *type_strings;
	int n_queries;
	unsigned types;
-	int rc;
	int opts;
-	enum {
-	OPT_stats = (1 << 4),
-	};
+	int rc;
+	int err;

	INIT_G();

@@ -827,61 +858,54 @@ int nslookup_main(int argc UNUSED_PARAM, char **argv)
	add_ns("127.0.0.1");
	}

-	for (rc = 0; rc < G.serv_count; rc++) {
-	int c = send_queries(&G.server[rc], queries, n_queries);
-	if (c > 0)
+	for (rc = 0; rc < G.serv_count;) {
+	int c;
+
+	c = send_queries(&G.server[rc], queries, n_queries);
+	if (c > 0) {
+	/* more than zero replies received */
+	if (opts & OPT_stats) {
+	printf("Replies:\t%d\n", G.server[rc].replies);
+	printf("Failures:\t%d\n\n", G.server[rc].failures);
+	}
	break;
+	//FIXME: we "break" even though some queries may still be not answered, and other servers may know them?
+	}
	/* c = 0: timed out waiting for replies */
	/* c < 0: error (message already printed) */
	rc++;
	if (rc >= G.serv_count) {
-	fprintf(stderr,
-	";; connection timed out; no servers could be reached\n\n");
+	//
+	// NB: bind-utils-9.11.3 behavior (all to stdout, not stderr):
+	//
+	// $ nslookup gmail.com 8.8.8.8
+	// ;; connection timed out; no servers could be reached
+	//
+	// $ nslookup -s gmail.com 8.8.8.8; echo EXITCODE:$?
+	// <~10 sec>
+	// ;; Connection to 8.8.8.8#53(8.8.8.8) for gmail.com failed: timed out.
+	// <~10 sec>
+	// ;; Connection to 8.8.8.8#53(8.8.8.8) for gmail.com failed: timed out.
+	// <~10 sec>
+	// ;; connection timed out; no servers could be reached
+	// ;; Connection to 8.8.8.8#53(8.8.8.8) for gmail.com failed: timed out.
+	// <empty line>
+	// EXITCODE:1
+	// $ _
+	printf(";; connection timed out; no servers could be reached\n\n");
	return EXIT_FAILURE;
	}
	}

-	printf("Server:\t\t%s\n", G.server[rc].name);
-	printf("Address:\t%s\n", xmalloc_sockaddr2dotted(&G.server[rc].lsa->u.sa));
-	/* In "Address", bind-utils-9.11.3 show port after a hash: "1.2.3.4#53" */
-	/* Should we do the same? */
-
-	if (opts & OPT_stats) {
-	printf("Replies:\t%d\n", G.server[rc].replies);
-	printf("Failures:\t%d\n", G.server[rc].failures);
-	}
-	printf("\n");
-
+	err = 0;
	for (rc = 0; rc < n_queries; rc++) {
-	int c;
-
-	if (opts & OPT_stats) {
-	printf("Query #%d completed in %ums:\n", rc, queries[rc].latency);
-	}
-
-	if (queries[rc].rcode != 0) {
-	printf("** server can't find %s: %s\n", queries[rc].name,
-	rcodes[queries[rc].rcode]);
-	continue;
-	}
-
-	c = 0;
-	if (queries[rc].rlen) {
-	HEADER *header;
-
-	header = (HEADER *)queries[rc].reply;
-	if (!header->aa)
-	printf("Non-authoritative answer:\n");
-	c = parse_reply(queries[rc].reply, queries[rc].rlen);
-	}
-
-	if (c == 0)
+	if (queries[rc].rlen == 0) {
	printf("*** Can't find %s: No answer\n", queries[rc].name);
-	else if (c < 0)
-	printf("*** Can't find %s: Parse error\n", queries[rc].name);
-
-	bb_putchar('\n');
+	err = 1;
+	}
	}
+	if (err)
+	bb_putchar('\n'); /* should this affect exicode too? */

	if (ENABLE_FEATURE_CLEAN_UP) {
	free(ns);