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net/dhcp: Allow receiving DHCP OFFER and ACK packets

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In respone to a BOOTREQUEST packet a BOOTP server would answer with a BOOTREPLY
packet, which ends the conversation for good. DHCP uses a 4-way handshake,
where the initial server respone is an OFFER, which has to be answered with
REQUEST by the client again, only to be completed by an ACKNOWLEDGE packet
from the server.

Teach the grub_net_process_dhcp() function to deal with OFFER packets,
and treat ACK packets the same es BOOTREPLY packets.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Andrei Borzenkov 2019-03-07 15:14:14 +00:00 committed by Daniel Kiper
parent 93289dc67c
commit 5a365fed87
2 changed files with 71 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

80
grub-core/net/bootp.c
View file

@ -30,6 +30,21 @@ enum
GRUB_DHCP_OPT_OVERLOAD_FILE = 1,
GRUB_DHCP_OPT_OVERLOAD_SNAME = 2,
};
enum
{
GRUB_DHCP_MESSAGE_UNKNOWN,
GRUB_DHCP_MESSAGE_DISCOVER,
GRUB_DHCP_MESSAGE_OFFER,
GRUB_DHCP_MESSAGE_REQUEST,
GRUB_DHCP_MESSAGE_DECLINE,
GRUB_DHCP_MESSAGE_ACK,
GRUB_DHCP_MESSAGE_NAK,
GRUB_DHCP_MESSAGE_RELEASE,
GRUB_DHCP_MESSAGE_INFORM,
};
/* Max timeout when waiting for BOOTP/DHCP reply */
#define GRUB_DHCP_MAX_PACKET_TIMEOUT 32
#define GRUB_BOOTP_MAX_OPTIONS_SIZE 64
@ -443,22 +458,59 @@ grub_net_process_dhcp (struct grub_net_buff *nb,
struct grub_net_card *card = iface->card;
const struct grub_net_bootp_packet *bp = (const struct grub_net_bootp_packet *) nb->data;
grub_size_t size = nb->tail - nb->data;
const grub_uint8_t *opt;
grub_uint8_t opt_len, type;
grub_uint32_t srv_id = 0;
name = grub_xasprintf ("%s:dhcp", card->name);
if (!name)
{
grub_print_error ();
return;
}
grub_net_configure_by_dhcp_ack (name, card, 0, bp, size, 0, 0, 0);
grub_free (name);
if (grub_errno)
grub_print_error ();
opt = find_dhcp_option (bp, size, GRUB_NET_DHCP_MESSAGE_TYPE, &opt_len);
if (opt && opt_len == 1)
type = *opt;
else
if (grub_memcmp (iface->name, card->name, grub_strlen (card->name)) == 0 &&
grub_memcmp (iface->name + grub_strlen (card->name),
":dhcp_tmp", sizeof (":dhcp_tmp") - 1) == 0)
grub_net_network_level_interface_unregister (iface);
type = GRUB_DHCP_MESSAGE_UNKNOWN;
opt = find_dhcp_option (bp, size, GRUB_NET_DHCP_SERVER_IDENTIFIER, &opt_len);
if (opt && opt_len == sizeof (srv_id))
srv_id = grub_get_unaligned32 (opt);
/*
* If we received BOOTP reply or DHCPACK, proceed with configuration.
* Otherwise store offered address and server id for later processing
* of DHCPACK.
* xid and srv_id are stored in network order so do not need conversion.
*/
if ((!iface->srv_id && type == GRUB_DHCP_MESSAGE_UNKNOWN)
|| (iface->srv_id && type == GRUB_DHCP_MESSAGE_ACK
&& bp->ident == iface->xid
&& srv_id == iface->srv_id))
{
name = grub_xasprintf ("%s:dhcp", card->name);
if (!name)
{
grub_print_error ();
return;
}
grub_net_configure_by_dhcp_ack (name, card, 0, bp, size, 0, 0, 0);
grub_free (name);
if (grub_errno)
grub_print_error ();
else
grub_net_network_level_interface_unregister (iface);
}
else if (!iface->srv_id && type == GRUB_DHCP_MESSAGE_OFFER && srv_id)
{
iface->srv_id = srv_id;
iface->my_ip = bp->your_ip;
/* Reset retransmission timer */
iface->dhcp_tmo = iface->dhcp_tmo_left = 1;
}
else if (iface->srv_id && type == GRUB_DHCP_MESSAGE_NAK
&& bp->ident == iface->xid
&& srv_id == iface->srv_id)
{
iface->xid = iface->srv_id = iface->my_ip = 0;
/* Reset retransmission timer */
iface->dhcp_tmo = iface->dhcp_tmo_left = 1;
}
}
static char

5
include/grub/net.h
View file

@ -292,6 +292,9 @@ struct grub_net_network_level_interface
struct grub_net_bootp_packet *dhcp_ack;
grub_size_t dhcp_acklen;
grub_uint16_t vlantag;
grub_uint32_t xid; /* DHCPv4 transaction id */
grub_uint32_t srv_id; /* DHCPv4 server_identifier */
grub_uint32_t my_ip; /* DHCPv4 offered IP address */
unsigned dhcp_tmo_left; /* DHCPv4 running retransmission timeout */
unsigned dhcp_tmo; /* DHCPv4 current retransmission timeout */
void *data;
@ -460,6 +463,8 @@ enum
GRUB_NET_BOOTP_ROOT_PATH = 0x11,
GRUB_NET_BOOTP_EXTENSIONS_PATH = 0x12,
GRUB_NET_DHCP_OVERLOAD = 52,
GRUB_NET_DHCP_MESSAGE_TYPE = 53,
GRUB_NET_DHCP_SERVER_IDENTIFIER = 54,
GRUB_NET_DHCP_TFTP_SERVER_NAME = 66,
GRUB_NET_DHCP_BOOTFILE_NAME = 67,
GRUB_NET_BOOTP_END = 0xff