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net/dns: Fix lookup error when no IPv6 is returned

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When trying to resolve DNS names into IP addresses, the DNS code fails
from time to time with the following error:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
error: ../../grub-core/net/dns.c:688:no DNS record found.
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

This happens when both IPv4 and IPv6 queries are performed against the
DNS server (e.g. 8.8.8.8) but there is no IP returned for IPv6 query, as
shown below:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
grub> net_del_dns 192.168.122.1
grub> net_add_dns 8.8.8.8
grub> net_nslookup ipv4.test-ipv6.com
error: ../../grub-core/net/dns.c:688:no DNS record found.
grub> net_nslookup ipv4.test-ipv6.com
216.218.228.115
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

The root cause is the code exiting prematurely when the data->addresses
buffer has been allocated in recv_hook(), even if there was no address
returned last time recv_hook() executed.

Signed-off-by: Renaud Métrich <rmetrich@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Renaud Métrich 2023-05-03 12:21:31 +02:00 committed by Daniel Kiper
parent 52a02dd24d
commit 1be86fae15
1 changed files with 6 additions and 16 deletions
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22
grub-core/net/dns.c
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@ -261,7 +261,7 @@ recv_hook (grub_net_udp_socket_t sock __attribute__ ((unused)),
/* Code apparently assumed that only one packet is received as response.
We may get multiple responses due to network condition, so check here
and quit early. */
if (*data->addresses)
if (*data->naddresses)
goto out;
head = (struct dns_header *) nb->data;
@ -305,11 +305,7 @@ recv_hook (grub_net_udp_socket_t sock __attribute__ ((unused)),
grub_uint32_t ttl = 0;
grub_uint16_t length;
if (ptr >= nb->tail)
{
if (!*data->naddresses)
grub_free (*data->addresses);
goto out;
}
goto out;
ignored = !check_name (ptr, nb->data, nb->tail, data->name);
while (ptr < nb->tail && !((*ptr & 0xc0) || *ptr == 0))
ptr += *ptr + 1;
@ -317,11 +313,7 @@ recv_hook (grub_net_udp_socket_t sock __attribute__ ((unused)),
ptr++;
ptr++;
if (ptr + 10 >= nb->tail)
{
if (!*data->naddresses)
grub_free (*data->addresses);
goto out;
}
goto out;
if (*ptr++ != 0)
ignored = 1;
class = *ptr++;
@ -337,11 +329,7 @@ recv_hook (grub_net_udp_socket_t sock __attribute__ ((unused)),
length = *ptr++ << 8;
length |= *ptr++;
if (ptr + length > nb->tail)
{
if (!*data->naddresses)
grub_free (*data->addresses);
goto out;
}
goto out;
if (!ignored)
{
if (ttl_all > ttl)
@ -428,6 +416,8 @@ recv_hook (grub_net_udp_socket_t sock __attribute__ ((unused)),
out:
grub_netbuff_free (nb);
grub_free (redirect_save);
if (!*data->naddresses)
grub_free (*data->addresses);
return GRUB_ERR_NONE;
}