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device: refactor generate_duid_from_machine_id() to have a straight forward code path

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Previously, there were two blocks

  if (NM_IN_SET (duid, "ll", "llt")
     preprocess_hwaddr()
  else if (NM_IN_SET (duid, "stable-ll", "stable-llt", "stable-uuid"))
     preprecess_stable_id()

  if (nm_streq (duid, "ll")
     generate_ll()
  else if (nm_streq (duid, "llt"))
     generate_llt()
  else if (nm_streq (duid, "stable-ll")
     generate_stable_ll()
  ...

That is, the latter block depends on the execution of the previous
block, while the previous block is guarded by a particular condition,
slighlty different than the condition in the later block.

It is confusing to follow. Instead, check for our cases one by one, and
when we determined a particular DUID type, process it within the same block
of code. Now the code consists of individual blocks, that all end with a "goto
out*". That means, it's easier to understand the flow of the code.

Also, don't initialize duid_error variable and separate between
"out_error" and "out_good". This allows that the compiler gives
a warning if we missed ot initialize duid_error.
This commit is contained in:
Thomas Haller 2018-06-11 12:27:03 +02:00
parent 6d06a0e1b0
commit 374d147421
1 changed files with 59 additions and 46 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

105
src/devices/nm-device.c
View file

@ -7816,8 +7816,8 @@ dhcp6_get_duid (NMDevice *self, NMConnection *connection, GBytes *hwaddr, NMDhcp
NMSettingIPConfig *s_ip6;
const char *duid;
gs_free char *duid_default = NULL;
const char *duid_error = NULL;
GBytes *duid_out = NULL;
const char *duid_error;
GBytes *duid_out;
guint8 sha256_digest[32];
gsize len = sizeof (sha256_digest);
NMDhcpDuidEnforce duid_enforce = NM_DHCP_DUID_ENFORCE_ALWAYS;
@ -7834,29 +7834,49 @@ dhcp6_get_duid (NMDevice *self, NMConnection *connection, GBytes *hwaddr, NMDhcp
if (!duid || nm_streq (duid, "lease")) {
duid_enforce = NM_DHCP_DUID_ENFORCE_NEVER;
duid_out = generate_duid_from_machine_id ();
if (!duid_out)
if (!duid_out) {
duid_error = "failure to read machine-id";
goto end;
goto out_fail;
}
goto out_good;
}
if (!_nm_utils_dhcp_duid_valid (duid, &duid_out)) {
duid_error = "invalid duid";
goto end;
goto out_fail;
}
if (duid_out)
goto end;
goto out_good;
if (NM_IN_STRSET (duid, "ll", "llt")) {
if (!hwaddr) {
duid_error = "missing link-layer address";
goto end;
goto out_fail;
}
if (g_bytes_get_size (hwaddr) != ETH_ALEN) {
duid_error = "unsupported link-layer address";
goto end;
goto out_fail;
}
} else if (NM_IN_STRSET (duid, "stable-llt", "stable-ll", "stable-uuid")) {
if (nm_streq (duid, "ll")) {
duid_out = generate_duid_ll (g_bytes_get_data (hwaddr, NULL));
} else {
gint64 time;
time = nm_utils_secret_key_get_timestamp ();
if (!time) {
duid_error = "cannot retrieve the secret key timestamp";
goto out_fail;
}
duid_out = generate_duid_llt (g_bytes_get_data (hwaddr, NULL), time);
}
goto out_good;
}
if (NM_IN_STRSET (duid, "stable-ll", "stable-llt", "stable-uuid")) {
NMUtilsStableType stable_type;
const char *stable_id = NULL;
guint32 salted_header;
@ -7880,51 +7900,42 @@ dhcp6_get_duid (NMDevice *self, NMConnection *connection, GBytes *hwaddr, NMDhcp
g_checksum_get_digest (sum, sha256_digest, &len);
g_checksum_free (sum);
}
if (nm_streq (duid, "stable-ll")) {
duid_out = generate_duid_ll (sha256_digest);
} else if (nm_streq (duid, "stable-llt")) {
gint64 time;
#define EPOCH_DATETIME_THREE_YEARS (356 * 24 * 3600 * 3)
if (nm_streq0 (duid, "ll")) {
duid_out = generate_duid_ll (g_bytes_get_data (hwaddr, NULL));
} else if (nm_streq0 (duid, "llt")) {
gint64 time;
/* We want a variable time between the secret_key timestamp and three years
* before. Let's compute the time (in seconds) from 0 to 3 years; then we'll
* subtract it from the secret_key timestamp.
*/
time = nm_utils_secret_key_get_timestamp ();
if (!time) {
duid_error = "cannot retrieve the secret key timestamp";
goto out_fail;
}
/* don't use too old timestamps. They cannot be expressed in DUID-LLT and
* would all be truncated to zero. */
time = NM_MAX (time, EPOCH_DATETIME_200001010000 + EPOCH_DATETIME_THREE_YEARS);
time -= (unaligned_read_be32 (&sha256_digest[ETH_ALEN]) % EPOCH_DATETIME_THREE_YEARS);
time = nm_utils_secret_key_get_timestamp ();
if (!time) {
duid_error = "cannot retrieve the secret key timestamp";
goto end;
duid_out = generate_duid_llt (sha256_digest, time);
} else {
nm_assert (nm_streq (duid, "stable-uuid"));
duid_out = generate_duid_uuid (sha256_digest, len);
}
duid_out = generate_duid_llt (g_bytes_get_data (hwaddr, NULL), time);
} else if (nm_streq0 (duid, "stable-ll")) {
duid_out = generate_duid_ll (sha256_digest);
} else if (nm_streq0 (duid, "stable-llt")) {
gint64 time;
/* We want a variable time between the secret_key timestamp and three years
* before. Let's compute the time (in seconds) from 0 to 3 years; then we'll
* subtract it from the secret_key timestamp.
*/
time = nm_utils_secret_key_get_timestamp ();
if (!time) {
duid_error = "cannot retrieve the secret key timestamp";
goto end;
}
/* don't use too old timestamps. They cannot be expressed in DUID-LLT and
* would all be truncated to zero. */
time = NM_MAX (time, EPOCH_DATETIME_200001010000 + EPOCH_DATETIME_THREE_YEARS);
time -= (unaligned_read_be32 (&sha256_digest[ETH_ALEN]) % EPOCH_DATETIME_THREE_YEARS);
duid_out = generate_duid_llt (sha256_digest, time);
} else if (nm_streq0 (duid, "stable-uuid")) {
duid_out = generate_duid_uuid (sha256_digest, len);
goto out_good;
}
duid_error = "generation failed";
end:
if (!duid_out) {
g_return_val_if_reached (NULL);
out_fail:
nm_assert (!duid_out && duid_error);
{
guint8 uuid[16];
_LOGW (LOGD_IP6, "duid-gen (%s): %s. Fallback to random DUID-UUID.", duid, duid_error);
@ -7933,6 +7944,8 @@ end:
duid_out = generate_duid_uuid (uuid, sizeof (uuid));
}
out_good:
nm_assert (duid_out);
_LOGD (LOGD_IP6, "DUID gen: '%s' (%s)",
nm_dhcp_utils_duid_to_string (duid_out),
(duid_enforce == NM_DHCP_DUID_ENFORCE_ALWAYS) ? "enforcing" : "fallback");