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Added DNS header mask definitions.

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Currently, we do a lot of data munging with manual hex. This is ugly
and can lead to bugs. I defined the following:

_QR_MASK    0x8000U
_OP_MASK    0x7800U
_AA_MASK    0x0400U
_TC_MASK    0x0200U
_RD_MASK    0x0100U
_RA_MASK    0x0080U
_Z_MASK     0x0040U
_AD_MASK    0x0020U
_CD_MASK    0x0010U
_RCODE_MASK 0x000fU

So that we can more easily twiddle flags.

v2: make evdns flag masks unsigned literal
Closes: #756 (cherry-picked)
(cherry picked from commit fb134939160a4baad89fd4ab20c49afd617057e3)
This commit is contained in:
Nathan French 2019-02-07 11:43:14 -05:00 committed by Azat Khuzhin
parent d44eb473cd
commit fcdda24b3a
No known key found for this signature in database
GPG Key ID: B86086848EF8686D
1 changed files with 23 additions and 10 deletions
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33
evdns.c
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@ -863,6 +863,19 @@ reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct repl
&d->deferred); &d->deferred);
} }
#define _QR_MASK 0x8000U
#define _OP_MASK 0x7800U
#define _AA_MASK 0x0400U
#define _TC_MASK 0x0200U
#define _RD_MASK 0x0100U
#define _RA_MASK 0x0080U
#define _Z_MASK 0x0040U
#define _AD_MASK 0x0020U
#define _CD_MASK 0x0010U
#define _RCODE_MASK 0x000fU
#define _Z_MASK_DEPRECATED 0x0070U
/* this processes a parsed reply packet */ /* this processes a parsed reply packet */
static void static void
reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) { reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) {
@ -876,12 +889,12 @@ reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply)
ASSERT_LOCKED(req->base); ASSERT_LOCKED(req->base);
ASSERT_VALID_REQUEST(req); ASSERT_VALID_REQUEST(req);
if (flags & 0x020f || !reply || !reply->have_answer) { if (flags & (_RCODE_MASK | _TC_MASK) || !reply || !reply->have_answer) {
/* there was an error */ /* there was an error */
if (flags & 0x0200) { if (flags & _TC_MASK) {
error = DNS_ERR_TRUNCATED; error = DNS_ERR_TRUNCATED;
} else if (flags & 0x000f) { } else if (flags & _RCODE_MASK) {
u16 error_code = (flags & 0x000f) - 1; u16 error_code = (flags & _RCODE_MASK) - 1;
if (error_code > 4) { if (error_code > 4) {
error = DNS_ERR_UNKNOWN; error = DNS_ERR_UNKNOWN;
} else { } else {
@ -1046,8 +1059,8 @@ reply_parse(struct evdns_base *base, u8 *packet, int length) {
memset(&reply, 0, sizeof(reply)); memset(&reply, 0, sizeof(reply));
/* If it's not an answer, it doesn't correspond to any request. */ /* If it's not an answer, it doesn't correspond to any request. */
if (!(flags & 0x8000)) return -1; /* must be an answer */ if (!(flags & _QR_MASK)) return -1; /* must be an answer */
if ((flags & 0x020f) && (flags & 0x020f) != DNS_ERR_NOTEXIST) { if ((flags & (_RCODE_MASK|_TC_MASK)) && (flags & (_RCODE_MASK|_TC_MASK)) != DNS_ERR_NOTEXIST) {
/* there was an error and it's not NXDOMAIN */ /* there was an error and it's not NXDOMAIN */
goto err; goto err;
} }
@ -1236,8 +1249,8 @@ request_parse(u8 *packet, int length, struct evdns_server_port *port, struct soc
(void)additional; (void)additional;
(void)authority; (void)authority;
if (flags & 0x8000) return -1; /* Must not be an answer. */ if (flags & _QR_MASK) return -1; /* Must not be an answer. */
flags &= 0x0110; /* Only RD and CD get preserved. */ flags &= (_RD_MASK|_CD_MASK); /* Only RD and CD get preserved. */
server_req = mm_malloc(sizeof(struct server_request)); server_req = mm_malloc(sizeof(struct server_request));
if (server_req == NULL) return -1; if (server_req == NULL) return -1;
@ -1277,7 +1290,7 @@ request_parse(u8 *packet, int length, struct evdns_server_port *port, struct soc
port->refcnt++; port->refcnt++;
/* Only standard queries are supported. */ /* Only standard queries are supported. */
if (flags & 0x7800) { if (flags & _OP_MASK) {
evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL); evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL);
return -1; return -1;
} }
@ -1904,7 +1917,7 @@ evdns_server_request_format_response(struct server_request *req, int err)
/* Set response bit and error code; copy OPCODE and RD fields from /* Set response bit and error code; copy OPCODE and RD fields from
* question; copy RA and AA if set by caller. */ * question; copy RA and AA if set by caller. */
flags = req->base.flags; flags = req->base.flags;
flags |= (0x8000 | err); flags |= (_QR_MASK | err);
dnslabel_table_init(&table); dnslabel_table_init(&table);
APPEND16(req->trans_id); APPEND16(req->trans_id);