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Fix bug #52239: if a DNS request is denied by a DNS server, this DNS request shouldn't be stopped if there is another DNS server to try

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Apply improved version of Xiaodong Sun's patch
This commit is contained in:
Dirk Ziegelmeier 2017-11-13 22:51:08 +01:00
parent a56ea1b19f
commit 2c1a152880
1 changed files with 33 additions and 1 deletions
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34
src/core/dns.c
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@ -1139,6 +1139,24 @@ dns_correct_response(u8_t idx, u32_t ttl)
} }
} }
} }
/**
* Check whether there are other backup DNS servers available to try
*/
static u8_t
dns_backupserver_available(struct dns_table_entry *pentry)
{
u8_t ret = 0;
if (pentry) {
if ((pentry->server_idx + 1 < DNS_MAX_SERVERS) && !ip_addr_isany_val(dns_servers[pentry->server_idx + 1])) {
ret = 1;
}
}
return ret;
}
/** /**
* Receive input function for DNS response packets arriving for the dns UDP pcb. * Receive input function for DNS response packets arriving for the dns UDP pcb.
*/ */
@ -1169,7 +1187,7 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr,
/* Match the ID in the DNS header with the name table. */ /* Match the ID in the DNS header with the name table. */
txid = lwip_htons(hdr.id); txid = lwip_htons(hdr.id);
for (i = 0; i < DNS_TABLE_SIZE; i++) { for (i = 0; i < DNS_TABLE_SIZE; i++) {
const struct dns_table_entry *entry = &dns_table[i]; struct dns_table_entry *entry = &dns_table[i];
if ((entry->state == DNS_STATE_ASKING) && if ((entry->state == DNS_STATE_ASKING) &&
(entry->txid == txid)) { (entry->txid == txid)) {
@ -1226,6 +1244,20 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr,
/* Check for error. If so, call callback to inform. */ /* Check for error. If so, call callback to inform. */
if (hdr.flags2 & DNS_FLAG2_ERR_MASK) { if (hdr.flags2 & DNS_FLAG2_ERR_MASK) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", entry->name)); LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", entry->name));
/* if there is another backup DNS server to try
* then don't stop the DNS request
*/
if (dns_backupserver_available(entry)) {
/* avoid retrying the same server */
entry->retries = DNS_MAX_RETRIES-1;
entry->tmr = 1;
/* contact next available server for this entry */
dns_check_entry(i);
goto ignore_packet;
}
} else { } else {
while ((nanswers > 0) && (res_idx < p->tot_len)) { while ((nanswers > 0) && (res_idx < p->tot_len)) {
/* skip answer resource record's host name */ /* skip answer resource record's host name */