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nslookup: add support for search domains, closes 11161

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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>
This commit is contained in:
Denys Vlasenko 2018-08-01 19:42:46 +02:00
parent d01c9aa7ca
commit 9408978a43
1 changed files with 84 additions and 24 deletions
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108
networking/nslookup.c
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@ -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)) {
char *p, *arg;
p = strtok(line, " \t\n");
if (!p || strcmp(p, "nameserver") != 0)
continue;
p = strtok(NULL, " \t\n");
if (!p)
continue;
dbg("resolv_key:'%s'\n", p);
arg = strtok(NULL, "\n");
dbg("resolv_arg:'%s'\n", arg);
if (!arg)
continue;
add_ns(xstrdup(p));
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 (strcmp(p, "nameserver") != 0)
continue;
/* 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;