dnsd: add -s option. This allows (clumsy) operation with read dns servers

function                                             old     new   delta
packed_usage                                       26816   26886     +70
dnsd_main                                           1299    1303      +4

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/include/usage.h b/include/usage.h
index 109a35d058796d776471adf008edc9fc6ee2d1be..c2ffb6d6edb9474d16c22fd9bd0196274ee55c02 100644 (file)
--- a/include/usage.h
+++ b/include/usage.h
@@ -893,7 +893,7 @@
      "\n       -s SIZE         Buffer size" \
 
 #define dnsd_trivial_usage \
-       "[-c CONFFILE] [-t TTL_SEC] [-p PORT] [-i ADDR] [-d]"
+       "[-dvs] [-c CONFFILE] [-t TTL_SEC] [-p PORT] [-i ADDR]"
 #define dnsd_full_usage "\n\n" \
        "Small static DNS server daemon\n" \
      "\nOptions:" \
@@ -902,6 +902,11 @@
      "\n       -p PORT Listen on PORT" \
      "\n       -i ADDR Listen on ADDR" \
      "\n       -d      Daemonize" \
+     "\n       -v      Verbose" \
+     "\n       -s      Send successful replies only. Use this if you want" \
+     "\n               to use /etc/resolv.conf with two nameserver lines:" \
+     "\n                       nameserver DNSD_SERVER" \
+     "\n                       nameserver NORNAL_DNS_SERVER" \
 
 #define dos2unix_trivial_usage \
        "[OPTIONS] [FILE]"

diff --git a/networking/dnsd.c b/networking/dnsd.c
index 42deb1f3562a139df2ae8b5ef72f3fe362a267ca..e73e244b0767747bd97cde5dda4d03e6ad73397d 100644 (file)
--- a/networking/dnsd.c
+++ b/networking/dnsd.c
@@ -56,7 +56,8 @@ struct dns_entry {
        char name[1];
 };
 
-#define OPT_verbose (option_mask32)
+#define OPT_verbose (option_mask32 & 1)
+#define OPT_silent  (option_mask32 & 2)
 
 
 /*
@@ -351,10 +352,11 @@ static int process_packet(struct dns_entry *conf_data,
                uint32_t conf_ttl,
                uint8_t *buf)
 {
-       char *answstr;
        struct dns_head *head;
        struct type_and_class *unaligned_type_class;
+       const char *err_msg;
        char *query_string;
+       char *answstr;
        uint8_t *answb;
        uint16_t outr_rlen;
        uint16_t outr_flags;
@@ -365,12 +367,19 @@ static int process_packet(struct dns_entry *conf_data,
        head = (struct dns_head *)buf;
        if (head->nquer == 0) {
                bb_error_msg("packet has 0 queries, ignored");
-               return -1;
+               return 0; /* don't reply */
        }
-
        if (head->flags & htons(0x8000)) { /* QR bit */
                bb_error_msg("response packet, ignored");
-               return -1;
+               return 0; /* don't reply */
+       }
+       /* QR = 1 "response", RCODE = 4 "Not Implemented" */
+       outr_flags = htons(0x8000 | 4);
+       err_msg = NULL;
+       /* OPCODE != 0 "standard query" ? */
+       if ((head->flags & htons(0x7800)) != 0) {
+               err_msg = "opcode != 0";
+               goto empty_packet;
        }
 
        /* start of query string */
@@ -383,28 +392,16 @@ static int process_packet(struct dns_entry *conf_data,
        /* where to append answer block */
        answb = (void *)(unaligned_type_class + 1);
 
-       /* QR = 1 "response", RCODE = 4 "Not Implemented" */
-       outr_flags = htons(0x8000 | 4);
-
-       move_from_unaligned16(type, &unaligned_type_class->type);
-       if (type != htons(REQ_A) && type != htons(REQ_PTR)) {
-               /* we can't handle this query type */
-//TODO: handle REQ_AAAA (0x1c) requests
-               bb_error_msg("type %u is !REQ_A and !REQ_PTR%s",
-                               (int)ntohs(type),
-                               ", returning Not Implemented reply");
-               goto empty_packet;
-       }
        move_from_unaligned16(class, &unaligned_type_class->class);
        if (class != htons(1)) { /* not class INET? */
-               bb_error_msg("class != 1%s",
-                               ", returning Not Implemented reply");
+               err_msg = "class != 1";
                goto empty_packet;
        }
-       /* OPCODE != 0 "standard query" ? */
-       if ((head->flags & htons(0x7800)) != 0) {
-               bb_error_msg("opcode != 0%s",
-                               ", returning Not Implemented reply");
+       move_from_unaligned16(type, &unaligned_type_class->type);
+       if (type != htons(REQ_A) && type != htons(REQ_PTR)) {
+               /* we can't handle this query type */
+//TODO: happens all the time with REQ_AAAA (0x1c) requests - implement those?
+               err_msg = "type is !REQ_A and !REQ_PTR";
                goto empty_packet;
        }
 
@@ -425,8 +422,7 @@ static int process_packet(struct dns_entry *conf_data,
                /* QR = 1 "response"
                 * AA = 1 "Authoritative Answer"
                 * RCODE = 3 "Name Error" */
-               if (OPT_verbose)
-                       bb_error_msg("returning Name Error reply");
+               err_msg = "name is not found";
                outr_flags = htons(0x8000 | 0x0400 | 3);
                goto empty_packet;
        }
@@ -455,6 +451,16 @@ static int process_packet(struct dns_entry *conf_data,
        head->nansw = htons(1);
 
  empty_packet:
+       if ((outr_flags & htons(0xf)) != 0) { /* not a positive response */
+               if (OPT_verbose) {
+                       bb_error_msg("%s, %s",
+                               err_msg,
+                               OPT_silent ? "dropping query" : "sending error reply"
+                       );
+               }
+               if (OPT_silent)
+                       return 0;
+       }
        head->flags |= outr_flags;
        head->nauth = head->nadd = 0;
        head->nquer = htons(1); // why???
@@ -476,21 +482,20 @@ int dnsd_main(int argc UNUSED_PARAM, char **argv)
        uint16_t port = 53;
        uint8_t buf[MAX_PACK_LEN + 1];
 
-       opts = getopt32(argv, "vi:c:t:p:d", &listen_interface, &fileconf, &sttl, &sport);
-       //if (opts & 0x1) // -v
-       //if (opts & 0x2) // -i
-       //if (opts & 0x4) // -c
-       if (opts & 0x8) // -t
+       opts = getopt32(argv, "vsi:c:t:p:d", &listen_interface, &fileconf, &sttl, &sport);
+       //if (opts & (1 << 0)) // -v
+       //if (opts & (1 << 1)) // -s
+       //if (opts & (1 << 2)) // -i
+       //if (opts & (1 << 3)) // -c
+       if (opts & (1 << 4)) // -t
                conf_ttl = xatou_range(sttl, 1, 0xffffffff);
-       if (opts & 0x10) // -p
+       if (opts & (1 << 5)) // -p
                port = xatou_range(sport, 1, 0xffff);
-       if (opts & 0x20) { // -d
+       if (opts & (1 << 6)) { // -d
                bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS, argv);
                openlog(applet_name, LOG_PID, LOG_DAEMON);
                logmode = LOGMODE_SYSLOG;
        }
-       /* Clear all except "verbose" bit */
-       option_mask32 &= 1;
 
        conf_data = parse_conf_file(fileconf);