simplify memory management for dns answers: use a blob_buf to cache entries

[project/mdnsd.git] / dns.c

diff --git a/dns.c b/dns.c
index 4951774..fc93f4a 100644 (file)
--- a/dns.c
+++ b/dns.c
@@ -40,28 +40,27 @@
 #include "interface.h"
 
 static char name_buffer[MAX_NAME_LEN + 1];
+static struct blob_buf ans_buf;
 
 const char*
 dns_type_string(uint16_t type)
 {
-       switch (type) {
-       case TYPE_A:
-               return "A";
-
-       case TYPE_AAAA:
-               return "AAAA";
-
-       case TYPE_PTR:
-               return "PTR";
-
-       case TYPE_TXT:
-               return "TXT";
-
-       case TYPE_SRV:
-               return "SRV";
+       static const struct {
+               uint16_t type;
+               char str[5];
+       } type_str[] = {
+               { TYPE_A, "A" },
+               { TYPE_AAAA, "AAAA" },
+               { TYPE_PTR, "PTR" },
+               { TYPE_TXT, "TXT" },
+               { TYPE_SRV, "SRV" },
+               { TYPE_ANY, "ANY" },
+       };
+       int i;
 
-       case TYPE_ANY:
-               return "ANY";
+       for (i = 0; i < ARRAY_SIZE(type_str); i++) {
+               if (type == type_str[i].type)
+                       return type_str[i].str;
        }
 
        return "N/A";
@@ -114,25 +113,29 @@ struct dns_reply {
        char *buffer;
 };
 
-#define MAX_ANSWER     8
-static struct dns_reply dns_reply[1 + (MAX_ANSWER * 3)];
 static int dns_answer_cnt;
 
 void
 dns_init_answer(void)
 {
        dns_answer_cnt = 0;
+       blob_buf_init(&ans_buf, 0);
 }
 
 void
 dns_add_answer(int type, const uint8_t *rdata, uint16_t rdlength)
 {
-       struct dns_reply *a = &dns_reply[dns_answer_cnt];
-       if (dns_answer_cnt == MAX_ANSWER)
-               return;
-       a->rdata = memdup(rdata, rdlength);
-       a->type = type;
-       a->rdlength = rdlength;
+       struct blob_attr *attr;
+       struct dns_answer *a;
+
+       attr = blob_new(&ans_buf, 0, sizeof(*a) + rdlength);
+       a = blob_data(attr);
+       a->type = cpu_to_be16(type);
+       a->class = cpu_to_be16(1);
+       a->ttl = cpu_to_be32(announce_ttl);
+       a->rdlength = cpu_to_be16(rdlength);
+       memcpy(a + 1, rdata, rdlength);
+
        dns_answer_cnt++;
 }
 
@@ -140,9 +143,11 @@ void
 dns_send_answer(struct interface *iface, const char *answer)
 {
        uint8_t buffer[256];
+       struct blob_attr *attr;
        struct dns_header h = { 0 };
        struct iovec *iov;
-       int len, i;
+       int answer_len, rem;
+       int n_iov = 0;
 
        if (!dns_answer_cnt)
                return;
@@ -150,44 +155,32 @@ dns_send_answer(struct interface *iface, const char *answer)
        h.answers = __cpu_to_be16(dns_answer_cnt);
        h.flags = __cpu_to_be16(0x8400);
 
-       iov = alloca(sizeof(struct iovec) * ((dns_answer_cnt * 3) + 1));
-       iov[0].iov_base = &h;
-       iov[0].iov_len = sizeof(struct dns_header);
+       iov = alloca(sizeof(struct iovec) * ((dns_answer_cnt * 2) + 1));
 
-       for (i = 0; i < dns_answer_cnt; i++) {
-               struct dns_answer *a = &dns_reply[i].a;
-               int id = (i * 3) + 1;
+       iov[n_iov].iov_base = &h;
+       iov[n_iov].iov_len = sizeof(struct dns_header);
+       n_iov++;
 
-               memset(a, 0, sizeof(*a));
-               a->type = __cpu_to_be16(dns_reply[i].type);
-               a->class = __cpu_to_be16(1);
-               a->ttl = __cpu_to_be32(announce_ttl);
-               a->rdlength = __cpu_to_be16(dns_reply[i].rdlength);
-
-               len = dn_comp(answer, buffer, sizeof(buffer), NULL, NULL);
-               if (len < 1)
-                       return;
+       answer_len = dn_comp(answer, buffer, sizeof(buffer), NULL, NULL);
+       if (answer_len < 1)
+               return;
 
-               dns_reply[i].buffer = iov[id].iov_base = memdup(buffer, len);
-               iov[id].iov_len = len;
+       blob_for_each_attr(attr, ans_buf.head, rem) {
+               struct dns_answer *a = blob_data(attr);
 
-               iov[id + 1].iov_base = a;
-               iov[id + 1].iov_len = sizeof(struct dns_answer);
+               iov[n_iov].iov_base = buffer;
+               iov[n_iov].iov_len = answer_len;
+               n_iov++;
 
-               iov[id + 2].iov_base = dns_reply[i].rdata;
-               iov[id + 2].iov_len = dns_reply[i].rdlength;
+               iov[n_iov].iov_base = blob_data(attr);
+               iov[n_iov].iov_len = blob_len(attr);
+               n_iov++;
 
-               DBG(1, "A <- %s %s\n", dns_type_string(dns_reply[i].type), answer);
+               DBG(1, "A <- %s %s\n", dns_type_string(be16_to_cpu(a->type)), answer);
        }
 
-       if (interface_send_packet(iface, iov, (dns_answer_cnt * 3) + 1) < 0)
+       if (interface_send_packet(iface, iov, n_iov) < 0)
                fprintf(stderr, "failed to send question\n");
-
-       for (i = 0; i < dns_answer_cnt; i++) {
-               free(dns_reply[i].buffer);
-               free(dns_reply[i].rdata);
-       }
-       dns_answer_cnt = 0;
 }
 
 static int
@@ -334,8 +327,7 @@ parse_question(struct interface *iface, char *name, struct dns_question *q)
 
        switch (q->type) {
        case TYPE_ANY:
-               host = service_name("local");
-               if (!strcmp(name, host))
+               if (!strcmp(name, mdns_hostname_local))
                        service_reply(iface, NULL);
                break;
 
@@ -349,7 +341,7 @@ parse_question(struct interface *iface, char *name, struct dns_question *q)
                host = strstr(name, ".local");
                if (host)
                        *host = '\0';
-               if (!strcmp(hostname, name))
+               if (!strcmp(mdns_hostname, name))
                        service_reply_a(iface, q->type);
                break;
        };