dnsd: fix one big-endian goof; add a TODO about RA bit

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

2 files changed, 26 insertions, 18 deletions

diff --git a/include/platform.h b/include/platform.h
index dcc61a77b..a134a9e42 100644
--- a/include/platform.h
+++ b/include/platform.h
@@ -208,6 +208,7 @@ typedef uint32_t bb__aliased_uint32_t FIX_ALIASING;
 # define move_from_unaligned_int(v, intp) ((v) = *(bb__aliased_int*)(intp))
 # define move_from_unaligned16(v, u16p) ((v) = *(bb__aliased_uint16_t*)(u16p))
 # define move_from_unaligned32(v, u32p) ((v) = *(bb__aliased_uint32_t*)(u32p))
+# define move_to_unaligned16(u16p, v)   (*(bb__aliased_uint16_t*)(u16p) = (v))
 # define move_to_unaligned32(u32p, v)   (*(bb__aliased_uint32_t*)(u32p) = (v))
 /* #elif ... - add your favorite arch today! */
 #else
@@ -215,6 +216,10 @@ typedef uint32_t bb__aliased_uint32_t FIX_ALIASING;
 # define move_from_unaligned_int(v, intp) (memcpy(&(v), (intp), sizeof(int)))
 # define move_from_unaligned16(v, u16p) (memcpy(&(v), (u16p), 2))
 # define move_from_unaligned32(v, u32p) (memcpy(&(v), (u32p), 4))
+# define move_to_unaligned16(u16p, v) do { \
+        uint16_t __t = (v); \
+        memcpy((u16p), &__t, 4); \
+} while (0)
 # define move_to_unaligned32(u32p, v) do { \
         uint32_t __t = (v); \
         memcpy((u32p), &__t, 4); \
diff --git a/networking/dnsd.c b/networking/dnsd.c
index 56ede3fca..91d66edcc 100644
--- a/networking/dnsd.c
+++ b/networking/dnsd.c
@@ -44,7 +44,7 @@ struct dns_head {
         uint16_t nauth;
         uint16_t nadd;
 };
-struct dns_prop {
+struct type_and_class {
         uint16_t type;
         uint16_t class;
 };
@@ -291,7 +291,7 @@ QCLASS  a two octet code that specifies the class of the query.
         (others are historic only)
         255 any class
 
-4.1.3. Resource record format
+4.1.3. Resource Record format
 
 The answer, authority, and additional sections all share the same format:
 a variable number of resource records, where the number of records
@@ -353,14 +353,14 @@ static int process_packet(struct dns_entry *conf_data,
 {
         char *answstr;
         struct dns_head *head;
-        struct dns_prop *unaligned_qprop;
+        struct type_and_class *unaligned_type_class;
         char *query_string;
         uint8_t *answb;
         uint16_t outr_rlen;
         uint16_t outr_flags;
         uint16_t type;
         uint16_t class;
-        int querystr_len;
+        int query_len;
 
         head = (struct dns_head *)buf;
         if (head->nquer == 0) {
@@ -376,22 +376,22 @@ static int process_packet(struct dns_entry *conf_data,
         /* start of query string */
         query_string = (void *)(head + 1);
         /* caller guarantees strlen is <= MAX_PACK_LEN */
-        querystr_len = strlen(query_string) + 1;
+        query_len = strlen(query_string) + 1;
         /* may be unaligned! */
-        unaligned_qprop = (void *)(query_string + querystr_len);
-        querystr_len += sizeof(unaligned_qprop);
+        unaligned_type_class = (void *)(query_string + query_len);
+        query_len += sizeof(unaligned_type_class);
         /* where to append answer block */
-        answb = (void *)(unaligned_qprop + 1);
+        answb = (void *)(unaligned_type_class + 1);
 
         /* QR = 1 "response", RCODE = 4 "Not Implemented" */
         outr_flags = htons(0x8000 | 4);
 
-        move_from_unaligned16(type, &unaligned_qprop->type);
+        move_from_unaligned16(type, &unaligned_type_class->type);
         if (type != htons(REQ_A) && type != htons(REQ_PTR)) {
                 /* we can't handle the query type */
                 goto empty_packet;
         }
-        move_from_unaligned16(class, &unaligned_qprop->class);
+        move_from_unaligned16(class, &unaligned_type_class->class);
         if (class != htons(1)) { /* not class INET? */
                 goto empty_packet;
         }
@@ -408,11 +408,11 @@ static int process_packet(struct dns_entry *conf_data,
         answstr = table_lookup(conf_data, type, query_string);
         outr_rlen = 4;
         if (answstr && type == htons(REQ_PTR)) {
-                /* return a host name */
+                /* returning a host name */
                 outr_rlen = strlen(answstr) + 1;
         }
         if (!answstr
-         || (unsigned)(answb - buf) + querystr_len + 4 + 2 + outr_rlen > MAX_PACK_LEN
+         || (unsigned)(answb - buf) + query_len + 4 + 2 + outr_rlen > MAX_PACK_LEN
         ) {
                 /* QR = 1 "response"
                  * AA = 1 "Authoritative Answer"
@@ -421,20 +421,23 @@ static int process_packet(struct dns_entry *conf_data,
                 goto empty_packet;
         }
 
-        /* copy query block to answer block */
-        memcpy(answb, query_string, querystr_len);
-        answb += querystr_len;
-        /* append answer Resource Record */
+        /* Append answer Resource Record */
+        memcpy(answb, query_string, query_len); /* name, type, class */
+        answb += query_len;
         move_to_unaligned32((uint32_t *)answb, htonl(conf_ttl));
         answb += 4;
-        move_to_unaligned32((uint16_t *)answb, htons(outr_rlen));
+        move_to_unaligned16((uint16_t *)answb, htons(outr_rlen));
         answb += 2;
         memcpy(answb, answstr, outr_rlen);
         answb += outr_rlen;
 
         /* QR = 1 "response",
          * AA = 1 "Authoritative Answer",
-         * RCODE = 0 "success" */
+         * TODO: need to set RA bit 0x80? One user says nslookup complains
+         * "Got recursion not available from SERVER, trying next server"
+         * "** server can't find HOSTNAME"
+         * RCODE = 0 "success"
+         */
         outr_flags = htons(0x8000 | 0x0400 | 0);
         /* we have one answer */
         head->nansw = htons(1);