[PATCH 11/31] rwrap: Recursively add additional data
Andreas Schneider
asn at samba.org
Wed Dec 3 07:45:07 MST 2014
From: Jakub Hrozek <jakub.hrozek at gmail.com>
Change how we construct the fake answer such that the header and
question are added first, then the answers and finally additional data.
Signed-off-by: Jakub Hrozek <jakub.hrozek at gmail.com>
Reviewed-by: Andreas Schneider <asn at samba.org>
Reviewed-by: Guenther Deschner <gd at samba.org>
Signed-off-by: Andreas Schneider <asn at samba.org>
---
lib/resolv_wrapper/resolv_wrapper.c | 139 ++++++++++++++++++++++++++++++------
1 file changed, 119 insertions(+), 20 deletions(-)
diff --git a/lib/resolv_wrapper/resolv_wrapper.c b/lib/resolv_wrapper/resolv_wrapper.c
index ea13aa6..69f4484 100644
--- a/lib/resolv_wrapper/resolv_wrapper.c
+++ b/lib/resolv_wrapper/resolv_wrapper.c
@@ -427,6 +427,7 @@ static ssize_t rwrap_fake_a(struct rwrap_fake_rr *rr,
"Malformed record, no or wrong value!\n");
return -1;
}
+ RWRAP_LOG(RWRAP_LOG_TRACE, "Adding A RR");
resp_size = rwrap_fake_rdata_common(ns_t_a, sizeof(struct in_addr), rr->key,
anslen, &a);
@@ -451,6 +452,7 @@ static ssize_t rwrap_fake_aaaa(struct rwrap_fake_rr *rr,
"Malformed record, no or wrong value!\n");
return -1;
}
+ RWRAP_LOG(RWRAP_LOG_TRACE, "Adding AAAA RR");
resp_size = rwrap_fake_rdata_common(ns_t_aaaa, sizeof(struct in6_addr),
rr->key, anslen, &a);
@@ -478,6 +480,7 @@ static ssize_t rwrap_fake_srv(struct rwrap_fake_rr *rr,
"Malformed record, no or wrong value!\n");
return -1;
}
+ RWRAP_LOG(RWRAP_LOG_TRACE, "Adding SRV RR");
rdata_size = 3 * sizeof(uint16_t);
/* Prepare the data to write */
@@ -520,6 +523,7 @@ static ssize_t rwrap_fake_soa(struct rwrap_fake_rr *rr,
"Malformed record, no or wrong value!\n");
return -1;
}
+ RWRAP_LOG(RWRAP_LOG_TRACE, "Adding SOA RR");
rdata_size = 5 * sizeof(uint16_t);
compressed_ns_len = ns_name_compress(rr->rrdata.soa_rec.nameserver,
@@ -571,6 +575,7 @@ static ssize_t rwrap_fake_cname(struct rwrap_fake_rr *rr,
"Malformed record, no or wrong value!\n");
return -1;
}
+ RWRAP_LOG(RWRAP_LOG_TRACE, "Adding CNAME RR");
/* Prepare the data to write */
rdata_size = ns_name_compress(rr->rrdata.cname_rec,
@@ -755,41 +760,78 @@ static ssize_t rwrap_fake_empty(int type,
return resp_data;
}
-static ssize_t rwrap_fake_answer(struct rwrap_fake_rr *rrs,
- uint8_t *answer,
- size_t anslen)
+static inline bool rwrap_known_type(int type)
+{
+ switch (type) {
+ case ns_t_a:
+ case ns_t_aaaa:
+ case ns_t_srv:
+ case ns_t_soa:
+ case ns_t_cname:
+ return true;
+ }
+
+ return false;
+}
+static int rwrap_ancount(struct rwrap_fake_rr *rrs, int qtype)
{
- ssize_t resp_data;
- size_t remaining = anslen;
+ int i;
+ int ancount = 0;
- resp_data = rwrap_fake_header(&answer, remaining, 1, 0);
- if (resp_data < 0) {
- return -1;
+ /* Include all RRs in the stack until the sought type
+ * in the answer section. This is the case i.e. when looking
+ * up an A record but the name points to a CNAME
+ */
+ for (i = 0; i < RWRAP_MAX_RECURSION; i++) {
+ ancount++;
+
+ if (rwrap_known_type(rrs[i].type) &&
+ rrs[i].type == qtype) {
+ break;
+ }
}
- remaining -= resp_data;
- resp_data += rwrap_fake_question(rrs->key, rrs->type, &answer, remaining);
- if (resp_data < 0) {
- return -1;
+ /* Return 0 records if the sought type wasn't in the stack */
+ return i < RWRAP_MAX_RECURSION ? ancount : 0;
+}
+
+static int rwrap_arcount(struct rwrap_fake_rr *rrs, int ancount)
+{
+ int i;
+ int arcount = 0;
+
+ /* start from index ancount */
+ for (i = ancount; i < RWRAP_MAX_RECURSION; i++) {
+ if (rwrap_known_type(rrs[i].type)) {
+ arcount++;
+ }
}
- remaining -= resp_data;
- switch (rrs->type) {
+ return arcount;
+}
+
+static ssize_t rwrap_add_rr(struct rwrap_fake_rr *rr,
+ uint8_t *answer,
+ size_t anslen)
+{
+ ssize_t resp_data;
+
+ switch (rr->type) {
case ns_t_a:
- resp_data += rwrap_fake_a(rrs, answer, anslen);
+ resp_data = rwrap_fake_a(rr, answer, anslen);
break;
case ns_t_aaaa:
- resp_data += rwrap_fake_aaaa(rrs, answer, anslen);
+ resp_data = rwrap_fake_aaaa(rr, answer, anslen);
break;
case ns_t_srv:
- resp_data += rwrap_fake_srv(rrs, answer, anslen);
+ resp_data = rwrap_fake_srv(rr, answer, anslen);
break;
case ns_t_soa:
- resp_data += rwrap_fake_soa(rrs, answer, anslen);
+ resp_data = rwrap_fake_soa(rr, answer, anslen);
break;
case ns_t_cname:
- resp_data += rwrap_fake_cname(rrs, answer, anslen);
+ resp_data = rwrap_fake_cname(rr, answer, anslen);
break;
default:
return -1;
@@ -798,6 +840,63 @@ static ssize_t rwrap_fake_answer(struct rwrap_fake_rr *rrs,
return resp_data;
}
+static ssize_t rwrap_fake_answer(struct rwrap_fake_rr *rrs,
+ int type,
+ uint8_t *answer,
+ size_t anslen)
+
+{
+ ssize_t resp_data;
+ ssize_t rrlen;
+ size_t remaining = anslen;
+ int ancount;
+ int arcount;
+ int i;
+
+ ancount = rwrap_ancount(rrs, type);
+ arcount = rwrap_arcount(rrs, ancount);
+ RWRAP_LOG(RWRAP_LOG_TRACE,
+ "Got %d answers and %d additional records\n", ancount, arcount);
+
+ resp_data = rwrap_fake_header(&answer, remaining, ancount, arcount);
+ if (resp_data < 0) {
+ return -1;
+ }
+ remaining -= resp_data;
+
+ resp_data += rwrap_fake_question(rrs->key, rrs->type, &answer, remaining);
+ if (resp_data < 0) {
+ return -1;
+ }
+ remaining -= resp_data;
+
+ /* answer */
+ for (i = 0; i < ancount; i++) {
+ rrlen = rwrap_add_rr(&rrs[i], answer, remaining);
+ if (rrlen < 0) {
+ return -1;
+ }
+ remaining -= rrlen;
+ answer += rrlen;
+ resp_data += rrlen;
+ }
+
+ /* add authoritative NS here? */
+
+ /* additional records */
+ for (i = ancount; i < ancount + arcount; i++) {
+ rrlen = rwrap_add_rr(&rrs[i], answer, remaining);
+ if (rrlen < 0) {
+ return -1;
+ }
+ remaining -= rrlen;
+ answer += rrlen;
+ resp_data += rrlen;
+ }
+
+ return resp_data;
+}
+
/* Reads in a file in the following format:
* TYPE RDATA
*
@@ -835,7 +934,7 @@ static int rwrap_res_fake_hosts(const char *hostfile,
case 0:
RWRAP_LOG(RWRAP_LOG_TRACE,
"Found record for [%s]\n", query_name);
- resp_size = rwrap_fake_answer(rrs, answer, anslen);
+ resp_size = rwrap_fake_answer(rrs, type, answer, anslen);
break;
case ENOENT:
RWRAP_LOG(RWRAP_LOG_TRACE,
--
2.1.3
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