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r11495@Kushana: nickm | 2006-12-11 19:11:14 -0500

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More evdns: tab fixes.  Dont make users worry about flags.  Set truncated flag correctly when generating responses, rather than just bailing out.


svn:r9084
This commit is contained in:
Nick Mathewson 2006-12-12 02:56:41 +00:00
parent abc1304aef
commit d22deb61d6
3 changed files with 57 additions and 30 deletions
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3
doc/TODO
View File

@ -92,6 +92,7 @@ N - DNS improvements
. Asynchronous DNS
o Document and rename SearchDomains, ResolvConf options
D Make API closer to getaddrinfo()
- Teach evdns about ipv6.
- Teach evdns to be able to listen for requests to be processed.
. Design interface.
- Rename stuff; current names suck.
@ -105,6 +106,8 @@ N - DNS improvements
o Queue responses when we see EAGAIN
o Retry responses after a while
o Be efficient about labels.
o Fix the interface for flags and flag handling.
o Generate truncated responses correctly.
- Comment everything.
- Clean up XXXX items
- Test

82
src/or/eventdns.c
View File

@ -407,7 +407,7 @@ struct server_request {
struct server_request *next_pending;
struct server_request *prev_pending;
u16 trans_id;
u16 trans_id;
struct evdns_server_port *port;
struct sockaddr_storage addr;
socklen_t addrlen;
@ -423,7 +423,7 @@ struct server_request {
char *response;
size_t response_len;
struct evdns_server_request base;
struct evdns_server_request base;
};
#define OFFSET_OF(st, member) ((off_t) (((char*)&((st*)0)->member)-(char*)0))
@ -970,14 +970,14 @@ reply_parse(u8 *packet, int length)
reply.type = req->request_type;
// skip over each question in the reply
// skip over each question in the reply
for (i = 0; i < questions; ++i) {
// the question looks like
// <label:name><u16:type><u16:class>
SKIP_NAME;
j += 4;
if (j >= length) return -1;
}
}
// now we have the answer section which looks like
// <label:name><u16:type><u16:class><u32:ttl><u16:len><data...>
@ -995,7 +995,7 @@ reply_parse(u8 *packet, int length)
// log("@%d, Name %s, type %d, class %d, j=%d", pre, tmp_name, (int)type, (int)class, j);
if (type == TYPE_A && class == CLASS_INET) {
if (type == TYPE_A && class == CLASS_INET) {
int addrcount, addrtocopy;
if (req->request_type != TYPE_A) {
j += datalength; continue;
@ -1064,6 +1064,8 @@ request_parse(u8 *packet, int length, struct evdns_server_port *port, struct soc
GET16(additional);
if (flags & 0x8000) return -1; // Must not be an answer.
if (flags & 0x7800) return -1; // only standard queries are supported
flags &= 0x0300; // Only TC and RD get preserved.
server_req = malloc(sizeof(struct server_request));
if (server_req == NULL) return -1;
@ -1384,7 +1386,7 @@ dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j,
#define APPEND16(x) do { \
if (j + 2 > (off_t)buf_len) \
return (-2); \
goto overflow; \
_t = htons(x); \
memcpy(buf + j, &_t, 2); \
j += 2; \
@ -1429,6 +1431,8 @@ dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j,
// in which case the zero is already there
if (!j || buf[j-1]) buf[j++] = 0;
return j;
overflow:
return (-2);
}
// Finds the length of a dns request for a DNS name of the given
@ -1454,13 +1458,12 @@ evdns_request_data_build(const char *const name, const int name_len, const u16 t
#define APPEND32(x) do { \
if (j + 4 > (off_t)buf_len) \
return (-1); \
goto overflow; \
_t32 = htonl(x); \
memcpy(buf + j, &_t32, 4); \
j += 4; \
} while (0)
APPEND16(trans_id);
APPEND16(0x0100); // standard query, recusion needed
APPEND16(1); // one question
@ -1477,6 +1480,8 @@ evdns_request_data_build(const char *const name, const int name_len, const u16 t
APPEND16(class);
return (int)j;
overflow:
return (-1);
}
// exported function
@ -1615,16 +1620,24 @@ evdns_request_add_cname_reply(struct evdns_server_request *req, const char *name
}
static int
evdns_request_response_format(struct server_request *req, int flags)
evdns_request_response_format(struct server_request *req, int err)
{
unsigned char buf[1500];
size_t buf_len = sizeof(buf);
off_t j = 0;
off_t j = 0, r;
u16 _t;
u32 _t32;
int i;
u16 flags;
struct dnslabel_table table;
if (err < 0 || err > 15) return -1;
/* Set response bit and error code; copy OPCODE and RD fields from
* question; copy RA and AA if set by caller. */
flags = req->base.flags;
flags |= (0x8000 | err);
dnslabel_table_init(&table); // XXXX need to call dnslable_table_clear.
APPEND16(req->trans_id);
APPEND16(flags);
@ -1643,7 +1656,7 @@ evdns_request_response_format(struct server_request *req, int flags)
APPEND16(req->base.questions[i]->class);
}
/* Add answer-like sections. */
/* Add answer, authority, and additional sections. */
for (i=0; i<3; ++i) {
struct server_request_item *item;
if (i==0)
@ -1653,9 +1666,10 @@ evdns_request_response_format(struct server_request *req, int flags)
else
item = req->additional;
while (item) {
j = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table);
if (j < 0)
return (int) j;
r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table);
if (r < 0)
goto overflow;
j = r;
APPEND16(item->type);
APPEND16(item->class);
@ -1664,15 +1678,16 @@ evdns_request_response_format(struct server_request *req, int flags)
off_t len_idx = j, name_start;
j += 2;
name_start = j;
j = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table);
if (j < 0)
return (int) j;
r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table);
if (r < 0)
goto overflow;
j = r;
_t = htons( (j-name_start) );
memcpy(buf+len_idx, &_t, 2);
} else {
APPEND16(item->datalen);
if (j+item->datalen > (off_t)buf_len)
return -1;
goto overflow;
memcpy(buf+j, item->data, item->datalen);
j += item->datalen;
}
@ -1680,11 +1695,20 @@ evdns_request_response_format(struct server_request *req, int flags)
}
}
req->response_len = j;
if (!(req->response = malloc(req->response_len)))
return -1;
memcpy(req->response, buf, req->response_len);
if (j > 512) {
overflow:
j = 512;
buf[3] |= 0x02; /* set the truncated bit. */
}
req->response_len = j;
if (!(req->response = malloc(req->response_len))) {
evdns_server_request_free_answers(req);
dnslabel_clear(&table);
return -1;
}
memcpy(req->response, buf, req->response_len);
evdns_server_request_free_answers(req);
dnslabel_clear(&table);
return 0;
@ -1692,13 +1716,13 @@ evdns_request_response_format(struct server_request *req, int flags)
// exported function
int
evdns_request_respond(struct evdns_server_request *_req, int flags)
evdns_request_respond(struct evdns_server_request *_req, int err)
{
struct server_request *req = TO_SERVER_REQUEST(_req);
struct evdns_server_port *port = req->port;
int r;
if (!req->response) {
if ((r = evdns_request_response_format(req, flags))<0)
if ((r = evdns_request_response_format(req, err))<0)
return r;
}
@ -1816,7 +1840,7 @@ evdns_request_timeout_callback(int fd, short events, void *arg) {
req->ns->timedout++;
if (req->ns->timedout > global_max_nameserver_timeout) {
req->ns->timedout = 0;
req->ns->timedout = 0;
nameserver_failed(req->ns, "request timed out.");
}
@ -2149,12 +2173,12 @@ request_new(int type, const char *name, int flags, evdns_callback_type callback,
// request data lives just after the header
req->request = ((u8 *) req) + sizeof(struct request);
// denotes that the request data shouldn't be free()ed
// denotes that the request data shouldn't be free()ed
req->request_appended = 1;
rlen = evdns_request_data_build(name, name_len, trans_id,
type, CLASS_INET, req->request, request_max_len);
type, CLASS_INET, req->request, request_max_len);
if (rlen < 0)
goto err1;
goto err1;
req->request_len = rlen;
req->trans_id = trans_id;
req->tx_count = 0;
@ -2933,7 +2957,7 @@ evdns_server_callback(struct evdns_server_request *req, void *data)
}
}
r = evdns_request_respond(req, 0x8000);
r = evdns_request_respond(req, 0);
if (r<0)
printf("eeek, couldn't send reply.\n");
}

2
src/or/eventdns.h
View File

@ -113,7 +113,7 @@ int evdns_request_add_aaaa_reply(struct evdns_server_request *req, const char *n
int evdns_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl);
int evdns_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl);
int evdns_request_respond(struct evdns_server_request *req, int flags);
int evdns_request_respond(struct evdns_server_request *req, int err);
int evdns_request_drop(struct evdns_server_request *req);
#endif // !EVENTDNS_H