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sd-dhcp-client: split out client_verify_message_header()

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This is not necessary to be called when a packet is received through the
RAW socket, but should not hurt anything.
This commit is contained in:
Yu Watanabe
2023-11-08 17:54:30 +09:00
parent 69f50bf35e
commit 7f42c66015
1 changed files with 51 additions and 45 deletions
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src/libsystemd-network/sd-dhcp-client.c
+51 -45
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@@ -2012,6 +2012,54 @@ static int client_restart(sd_dhcp_client *client) {
return 0;
}
static int client_verify_message_header(sd_dhcp_client *client, DHCPMessage *message, size_t len) {
const uint8_t *expected_chaddr = NULL;
uint8_t expected_hlen = 0;
assert(client);
assert(message);
if (len < sizeof(DHCPMessage))
return log_dhcp_client_errno(client, SYNTHETIC_ERRNO(EBADMSG),
"Too small to be a DHCP message, ignoring.");
if (be32toh(message->magic) != DHCP_MAGIC_COOKIE)
return log_dhcp_client_errno(client, SYNTHETIC_ERRNO(EBADMSG),
"Not a DHCP message, ignoring.");
if (message->op != BOOTREPLY)
return log_dhcp_client_errno(client, SYNTHETIC_ERRNO(EBADMSG),
"Not a BOOTREPLY message, ignoring.");
if (message->htype != client->arp_type)
return log_dhcp_client_errno(client, SYNTHETIC_ERRNO(EBADMSG),
"Packet type does not match client type, ignoring.");
if (client->arp_type == ARPHRD_ETHER) {
expected_hlen = ETH_ALEN;
expected_chaddr = client->hw_addr.bytes;
}
if (message->hlen != expected_hlen)
return log_dhcp_client_errno(client, SYNTHETIC_ERRNO(EBADMSG),
"Received packet hlen (%u) does not match expected (%u), ignoring.",
message->hlen, expected_hlen);
if (memcmp_safe(message->chaddr, expected_chaddr, expected_hlen))
return log_dhcp_client_errno(client, SYNTHETIC_ERRNO(EBADMSG),
"Received chaddr does not match expected, ignoring.");
if (client->state != DHCP_STATE_BOUND &&
be32toh(message->xid) != client->xid)
/* in BOUND state, we may receive FORCERENEW with xid set by server,
so ignore the xid in this case */
return log_dhcp_client_errno(client, SYNTHETIC_ERRNO(EBADMSG),
"Received xid (%u) does not match expected (%u), ignoring.",
be32toh(message->xid), client->xid);
return 0;
}
static int client_handle_message(sd_dhcp_client *client, DHCPMessage *message, size_t len) {
DHCP_CLIENT_DONT_DESTROY(client);
int r;
@@ -2019,6 +2067,9 @@ static int client_handle_message(sd_dhcp_client *client, DHCPMessage *message, s
assert(client);
assert(message);
if (client_verify_message_header(client, message, len) < 0)
return 0;
switch (client->state) {
case DHCP_STATE_SELECTING:
@@ -2082,8 +2133,6 @@ static int client_receive_message_udp(
sd_dhcp_client *client = ASSERT_PTR(userdata);
_cleanup_free_ DHCPMessage *message = NULL;
const uint8_t *expected_chaddr = NULL;
uint8_t expected_hlen = 0;
ssize_t len, buflen;
int r;
@@ -2109,49 +2158,6 @@ static int client_receive_message_udp(
log_dhcp_client_errno(client, errno, "Could not receive message from UDP socket, ignoring: %m");
return 0;
}
if ((size_t) len < sizeof(DHCPMessage)) {
log_dhcp_client(client, "Too small to be a DHCP message: ignoring");
return 0;
}
if (be32toh(message->magic) != DHCP_MAGIC_COOKIE) {
log_dhcp_client(client, "Not a DHCP message: ignoring");
return 0;
}
if (message->op != BOOTREPLY) {
log_dhcp_client(client, "Not a BOOTREPLY message: ignoring");
return 0;
}
if (message->htype != client->arp_type) {
log_dhcp_client(client, "Packet type does not match client type");
return 0;
}
if (client->arp_type == ARPHRD_ETHER) {
expected_hlen = ETH_ALEN;
expected_chaddr = client->hw_addr.bytes;
}
if (message->hlen != expected_hlen) {
log_dhcp_client(client, "Unexpected packet hlen %d", message->hlen);
return 0;
}
if (expected_hlen > 0 && memcmp(&message->chaddr[0], expected_chaddr, expected_hlen)) {
log_dhcp_client(client, "Received chaddr does not match expected: ignoring");
return 0;
}
if (client->state != DHCP_STATE_BOUND &&
be32toh(message->xid) != client->xid) {
/* in BOUND state, we may receive FORCERENEW with xid set by server,
so ignore the xid in this case */
log_dhcp_client(client, "Received xid (%u) does not match expected (%u): ignoring",
be32toh(message->xid), client->xid);
return 0;
}
log_dhcp_client(client, "Received message from UDP socket, processing.");
r = client_handle_message(client, message, len);