fix(dns): Fix a bug of the seq number is overflow, if we don't have found an unused entry and table is full, use the oldest completed one.

Author: lhespress

third_party/lwip/core/dns.c

@@ -896,6 +896,17 @@ dns_enqueue(const char *name, dns_found_callback found, void *callback_arg)
  if ((dns_seqno - pEntry->seqno) > lseq) {
  lseq = dns_seqno - pEntry->seqno;
  lseqi = i;
+ } else {
+ if (pEntry->seqno >= (0xFF - DNS_TABLE_SIZE)) {
+ static u8 index = 0;
+ if ((pEntry->seqno - (0xFF - DNS_TABLE_SIZE)) == index) {
+ index ++;
+ lseqi = i;
+ if (index == DNS_TABLE_SIZE) {
+ index = 0;
+ }
+ }
+ }
  }
  }
  }
@@ -918,13 +929,17 @@ dns_enqueue(const char *name, dns_found_callback found, void *callback_arg)
 
  /* fill the entry */
  pEntry->state = DNS_STATE_NEW;
- pEntry->seqno = dns_seqno++;
+ pEntry->seqno = dns_seqno;
  pEntry->found = found;
  pEntry->arg = callback_arg;
  namelen = LWIP_MIN(os_strlen(name), DNS_MAX_NAME_LENGTH-1);
  MEMCPY(pEntry->name, name, namelen);
  pEntry->name[namelen] = 0;
 
+ dns_seqno ++;
+ if (dns_seqno == 0xFF) {
+ dns_seqno = 0;
+ }
  /* force to send query without waiting timer */
  dns_check_entry(i);