Comment getsrvrr.

[doldaconnect.git] / lib / uilib.c

diff --git a/lib/uilib.c b/lib/uilib.c
index 2bd9575..26958a7 100644 (file)
--- a/lib/uilib.c
+++ b/lib/uilib.c
@@ -47,7 +47,9 @@
 #endif
 
 #include <doldaconnect/uilib.h>
-#include <doldaconnect/utils.h>
+#include <utils.h>
+
+#define DOLCON_SRV_NAME "_dolcon._tcp"
 
 #define RESP_END -1
 #define RESP_DSC 0
@@ -784,6 +786,10 @@ int dc_handlewrite(void)
 }
 
 #ifdef HAVE_RESOLVER
+/*
+ * It kind of sucks that libresolv doesn't have any DNS parsing
+ * routines. We'll have to do it manually.
+ */
 static char *readname(unsigned char *msg, unsigned char *eom, unsigned char **p)
 {
     char *name, *tname;
@@ -858,15 +864,10 @@ static int getsrvrr(char *name, char **host, int *port)
            return(-1);
     }
     /* res_querydomain doesn't work for some reason */
-    name2 = smalloc(strlen("_dolcon._tcp.") + strlen(name) + 2);
-    strcpy(name2, "_dolcon._tcp.");
-    strcat(name2, name);
-    len = strlen(name2);
-    if(name2[len - 1] != '.')
-    {
-       name2[len] = '.';
-       name2[len + 1] = 0;
-    }
+    if(name[strlen(name) - 1] == '.')
+       name2 = sprintf2("%s.%s", DOLCON_SRV_NAME, name);
+    else
+       name2 = sprintf2("%s.%s.", DOLCON_SRV_NAME, name);
     ret = res_query(name2, C_IN, T_SRV, buf, sizeof(buf));
     if(ret < 0)
     {
@@ -874,12 +875,20 @@ static int getsrvrr(char *name, char **host, int *port)
        return(-1);
     }
     eom = buf + ret;
+    /*
+     * Assume transaction ID is correct.
+     *
+     * Flags check: FA0F masks in request/response flag, opcode,
+     * truncated flag and status code, and ignores authoritativeness,
+     * recursion flags and DNSSEC and reserved bits.
+     */
     flags = (buf[2] << 8) + buf[3];
     if((flags & 0xfa0f) != 0x8000)
     {
        free(name2);
        return(-1);
     }
+    /* Skip the query entries */
     num = (buf[4] << 8) + buf[5];
     p = buf + 12;
     for(i = 0; i < num; i++)
@@ -889,8 +898,9 @@ static int getsrvrr(char *name, char **host, int *port)
            free(name2);
            return(-1);
        }
-       p += 4;
+       p += 4; /* Type and class */
     }
+    /* Parse answers */
     num = (buf[6] << 8) + buf[7];
     for(i = 0; i < num; i++)
     {
@@ -903,7 +913,7 @@ static int getsrvrr(char *name, char **host, int *port)
        type += *(p++);
        class = *(p++) << 8;
        class += *(p++);
-       p += 4;
+       p += 4; /* TTL */
        len = *(p++) << 8;
        len += *(p++);
        if((class == C_IN) && (type == T_SRV) && !strcmp(rrname, name2))