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dhcp: support endianness independent dhcp_identifier_set_iaid()

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The previous code did htole64() followed by unaligned_write_be32() (the
XOR and shift in between is endianness agnostic). That means, on every
architeture there is always exactly one byte swap and the iaid is
dependent on endianness.

Since dhcp_identifier_set_iaid() is part of the DUID generation
algorithm, this cannot be fixed without changing the client-id.
In particular, as the client-id already depends on the machine-id (and
is thus inherrently host-specific), it is better to stick to the current
behavior.

However, add a parameter to switch between old and new behaviour.
Since the new behavior is unused, the only real purpose of this
change is to self-document the oddity of the function.

Fixes: 933f9caeeb
This commit is contained in:
Thomas Haller
2018-11-12 19:08:35 +01:00
parent 43fc095532
commit 6d13616b9e
5 changed files with 37 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/libsystemd-network/dhcp-identifier.c
+18 -4
View File
@@ -148,12 +148,18 @@ int dhcp_identifier_set_duid_uuid(struct duid *duid, size_t *len) {
return 0;
}
int dhcp_identifier_set_iaid(int ifindex, uint8_t *mac, size_t mac_len, void *_id) {
int dhcp_identifier_set_iaid(
int ifindex,
const uint8_t *mac,
size_t mac_len,
bool legacy_unstable_byteorder,
void *_id) {
/* name is a pointer to memory in the sd_device struct, so must
* have the same scope */
_cleanup_(sd_device_unrefp) sd_device *device = NULL;
const char *name = NULL;
uint64_t id;
uint32_t id32;
if (detect_container() <= 0) {
/* not in a container, udev will be around */
@@ -179,10 +185,18 @@ int dhcp_identifier_set_iaid(int ifindex, uint8_t *mac, size_t mac_len, void *_i
/* fall back to MAC address if no predictable name available */
id = siphash24(mac, mac_len, HASH_KEY.bytes);
id = htole64(id);
id32 = (id & 0xffffffff) ^ (id >> 32);
/* fold into 32 bits */
unaligned_write_be32(_id, (id & 0xffffffff) ^ (id >> 32));
if (legacy_unstable_byteorder)
/* for historical reasons (a bug), the bits were swapped and thus
* the result was endianness dependant. Preserve that behavior. */
id32 = __bswap_32(id32);
else
/* the fixed behavior returns a stable byte order. Since LE is expected
* to be more common, swap the bytes on LE to give the same as legacy
* behavior. */
id32 = be32toh(id32);
unaligned_write_ne32(_id, id32);
return 0;
}
src/libsystemd-network/dhcp-identifier.h
+1 -1
View File
@@ -57,4 +57,4 @@ int dhcp_identifier_set_duid_llt(struct duid *duid, usec_t t, const uint8_t *add
int dhcp_identifier_set_duid_ll(struct duid *duid, const uint8_t *addr, size_t addr_len, uint16_t arp_type, size_t *len);
int dhcp_identifier_set_duid_en(struct duid *duid, size_t *len);
int dhcp_identifier_set_duid_uuid(struct duid *duid, size_t *len);
int dhcp_identifier_set_iaid(int ifindex, uint8_t *mac, size_t mac_len, void *_id);
int dhcp_identifier_set_iaid(int ifindex, const uint8_t *mac, size_t mac_len, bool legacy_unstable_byteorder, void *_id);
src/libsystemd-network/sd-dhcp-client.c
+3 -1
View File
@@ -371,6 +371,7 @@ static int dhcp_client_set_iaid_duid_internal(
if (iaid == 0) {
r = dhcp_identifier_set_iaid(client->ifindex, client->mac_addr,
client->mac_addr_len,
true,
&client->client_id.ns.iaid);
if (r < 0)
return r;
@@ -650,7 +651,8 @@ static int client_message_init(
client->client_id.type = 255;
r = dhcp_identifier_set_iaid(client->ifindex, client->mac_addr, client->mac_addr_len, &client->client_id.ns.iaid);
r = dhcp_identifier_set_iaid(client->ifindex, client->mac_addr, client->mac_addr_len,
true, &client->client_id.ns.iaid);
if (r < 0)
return r;
src/libsystemd-network/sd-dhcp6-client.c
+2 -2
View File
@@ -807,14 +807,14 @@ error:
static int client_ensure_iaid(sd_dhcp6_client *client) {
int r;
be32_t iaid;
uint32_t iaid;
assert(client);
if (client->ia_na.ia_na.id)
return 0;
r = dhcp_identifier_set_iaid(client->ifindex, client->mac_addr, client->mac_addr_len, &iaid);
r = dhcp_identifier_set_iaid(client->ifindex, client->mac_addr, client->mac_addr_len, true, &iaid);
if (r < 0)
return r;
src/libsystemd-network/test-dhcp-client.c
+13 -5
View File
@@ -156,7 +156,8 @@ static void test_checksum(void) {
}
static void test_dhcp_identifier_set_iaid(void) {
uint32_t iaid;
uint32_t iaid_legacy;
be32_t iaid;
int ifindex;
for (;;) {
@@ -169,11 +170,18 @@ static void test_dhcp_identifier_set_iaid(void) {
break;
}
assert_se(dhcp_identifier_set_iaid(ifindex, mac_addr, sizeof(mac_addr), &iaid) >= 0);
assert_se(dhcp_identifier_set_iaid(ifindex, mac_addr, sizeof(mac_addr), true, &iaid_legacy) >= 0);
assert_se(dhcp_identifier_set_iaid(ifindex, mac_addr, sizeof(mac_addr), false, &iaid) >= 0);
/* we expect, that the MAC address was hashed. Note that the value is in native
/* we expect, that the MAC address was hashed. The legacy value is in native
* endianness. */
assert_se(iaid == 0x8dde4ba8u);
assert_se(iaid_legacy == 0x8dde4ba8u);
assert_se(iaid == htole32(0x8dde4ba8u));
#if __BYTE_ORDER == __LITTLE_ENDIAN
assert_se(iaid == iaid_legacy);
#else
assert_se(iaid == __bswap_32(iaid_legacy));
#endif
}
static int check_options(uint8_t code, uint8_t len, const void *option, void *userdata) {
@@ -185,7 +193,7 @@ static int check_options(uint8_t code, uint8_t len, const void *option, void *us
size_t duid_len;
assert_se(dhcp_identifier_set_duid_en(&duid, &duid_len) >= 0);
assert_se(dhcp_identifier_set_iaid(42, mac_addr, ETH_ALEN, &iaid) >= 0);
assert_se(dhcp_identifier_set_iaid(42, mac_addr, ETH_ALEN, true, &iaid) >= 0);
assert_se(len == sizeof(uint8_t) + sizeof(uint32_t) + duid_len);
assert_se(len == 19);