nslookup: add support for search domains, closes 11161

function                                             old     new   delta
parse_resolvconf                                       -     311    +311
add_query_with_search                                  -     105    +105
nslookup_main                                        873     757    -116
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 0/1 up/down: 416/-116)          Total: 300 bytes

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

diff --git a/networking/nslookup.c b/networking/nslookup.c
index 3a614b0c6c60d89b09c2a8f5b98bd8bc535ec97e..e153eb585dcb72d81ba2eef7181a1de6193d1906 100644 (file)
--- a/networking/nslookup.c
+++ b/networking/nslookup.c
@@ -318,6 +318,8 @@ struct globals {
        unsigned serv_count;
        struct ns *server;
        struct query *query;
+       char *search;
+       smalluint have_search_directive;
 } FIX_ALIASING;
 #define G (*(struct globals*)bb_common_bufsiz1)
 #define INIT_G() do { \
@@ -667,24 +669,60 @@ static void parse_resolvconf(void)
 
        resolv = fopen("/etc/resolv.conf", "r");
        if (resolv) {
-               char line[128], *p;
+               char line[512]; /* "search" is defined to be up to 256 chars */
 
                while (fgets(line, sizeof(line), resolv)) {
-                       p = strtok(line, " \t\n");
+                       char *p, *arg;
 
-                       if (!p || strcmp(p, "nameserver") != 0)
+                       p = strtok(line, " \t\n");
+                       if (!p)
+                               continue;
+                       dbg("resolv_key:'%s'\n", p);
+                       arg = strtok(NULL, "\n");
+                       dbg("resolv_arg:'%s'\n", arg);
+                       if (!arg)
                                continue;
 
-                       p = strtok(NULL, " \t\n");
+                       if (strcmp(p, "domain") == 0) {
+                               /* domain DOM */
+                               if (!G.have_search_directive)
+                                       goto set_search;
+                               continue;
+                       }
+                       if (strcmp(p, "search") == 0) {
+                               /* search DOM1 DOM2... */
+                               G.have_search_directive = 1;
+ set_search:
+                               free(G.search);
+                               G.search = xstrdup(arg);
+                               dbg("search='%s'\n", G.search);
+                               continue;
+                       }
 
-                       if (!p)
+                       if (strcmp(p, "nameserver") != 0)
                                continue;
 
-                       add_ns(xstrdup(p));
+                       /* nameserver DNS */
+                       add_ns(xstrdup(arg));
                }
 
                fclose(resolv);
        }
+
+       if (!G.search) {
+               /* default search domain is domain part of hostname */
+               char *h = safe_gethostname();
+               char *d = strchr(h, '.');
+               if (d) {
+                       G.search = d + 1;
+                       dbg("search='%s' (from hostname)\n", G.search);
+               }
+               /* else free(h); */
+       }
+
+       /* Cater for case of "domain ." in resolv.conf */
+       if (G.search && LONE_CHAR(G.search, '.'))
+               G.search = NULL;
 }
 
 static void add_query(int type, const char *dname)
@@ -695,7 +733,7 @@ static void add_query(int type, const char *dname)
 
        count = G.query_count++;
 
-       G.query = xrealloc_vector(G.query, /*2=2^1:*/ 1, count);
+       G.query = xrealloc_vector(G.query, /*4=2^2:*/ 2, count);
        new_q = &G.query[count];
 
        dbg("new query#%u type %u for '%s'\n", count, type, dname);
@@ -709,6 +747,28 @@ static void add_query(int type, const char *dname)
        new_q->qlen = qlen;
 }
 
+static void add_query_with_search(int type, const char *dname)
+{
+       char *s;
+
+       if (type == T_PTR || !G.search || strchr(dname, '.')) {
+               add_query(type, dname);
+               return;
+       }
+
+       s = G.search;
+       for (;;) {
+               char *fullname, *e;
+
+               e = skip_non_whitespace(s);
+               fullname = xasprintf("%s.%.*s", dname, (int)(e - s), s);
+               add_query(type, fullname);
+               s = skip_whitespace(e);
+               if (!*s)
+                       break;
+       }
+}
+
 static char *make_ptr(const char *addrstr)
 {
        unsigned char addr[16];
@@ -833,6 +893,18 @@ int nslookup_main(int argc UNUSED_PARAM, char **argv)
                }
        }
 
+       /* Use given DNS server if present */
+       if (argv[1]) {
+               if (argv[2])
+                       bb_show_usage();
+               add_ns(argv[1]);
+       } else {
+               parse_resolvconf();
+               /* Fall back to localhost if we could not find NS in resolv.conf */
+               if (G.serv_count == 0)
+                       add_ns("127.0.0.1");
+       }
+
        if (types == 0) {
                /* No explicit type given, guess query type.
                 * If we can convert the domain argument into a ptr (means that
@@ -846,31 +918,19 @@ int nslookup_main(int argc UNUSED_PARAM, char **argv)
                if (ptr) {
                        add_query(T_PTR, ptr);
                } else {
-                       add_query(T_A, argv[0]);
+                       add_query_with_search(T_A, argv[0]);
 #if ENABLE_FEATURE_IPV6
-                       add_query(T_AAAA, argv[0]);
+                       add_query_with_search(T_AAAA, argv[0]);
 #endif
                }
        } else {
                int c;
                for (c = 0; c < ARRAY_SIZE(qtypes); c++) {
                        if (types & (1 << c))
-                               add_query(qtypes[c].type, argv[0]);
+                               add_query_with_search(qtypes[c].type, argv[0]);
                }
        }
 
-       /* Use given DNS server if present */
-       if (argv[1]) {
-               if (argv[2])
-                       bb_show_usage();
-               add_ns(argv[1]);
-       } else {
-               parse_resolvconf();
-               /* Fall back to localhost if we could not find NS in resolv.conf */
-               if (G.serv_count == 0)
-                       add_ns("127.0.0.1");
-       }
-
        for (rc = 0; rc < G.serv_count;) {
                int c;