2 files changed, 59 insertions, 0 deletions

diff --git a/src/libsystemd/sd-network/network-util.c b/src/libsystemd/sd-network/network-util.c
index f3d6061578..7c32a8ead1 100644
--- a/src/libsystemd/sd-network/network-util.c
+++ b/src/libsystemd/sd-network/network-util.c
@@ -1,9 +1,14 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 
+#include "sd-id128.h"
+
 #include "alloc-util.h"
 #include "arphrd-list.h"
+#include "device-util.h"
 #include "fd-util.h"
 #include "network-util.h"
+#include "siphash24.h"
+#include "sparse-endian.h"
 #include "string-table.h"
 #include "strv.h"
 
@@ -124,3 +129,52 @@ char *link_get_type_string(sd_device *device, unsigned short iftype) {
 
         return ascii_strlower(p);
 }
+
+const char *net_get_name_persistent(sd_device *device) {
+        const char *name, *field;
+
+        assert(device);
+
+        /* fetch some persistent data unique (on this machine) to this device */
+        FOREACH_STRING(field, "ID_NET_NAME_ONBOARD", "ID_NET_NAME_SLOT", "ID_NET_NAME_PATH", "ID_NET_NAME_MAC")
+                if (sd_device_get_property_value(device, field, &name) >= 0)
+                        return name;
+
+        return NULL;
+}
+
+#define HASH_KEY SD_ID128_MAKE(d3,1e,48,fa,90,fe,4b,4c,9d,af,d5,d7,a1,b1,2e,8a)
+
+int net_get_unique_predictable_data(sd_device *device, bool use_sysname, uint64_t *result) {
+        size_t l, sz = 0;
+        const char *name;
+        int r;
+        uint8_t *v;
+
+        assert(device);
+
+        /* net_get_name_persistent() will return one of the device names based on stable information about
+         * the device. If this is not available, we fall back to using the actual device name. */
+        name = net_get_name_persistent(device);
+        if (!name && use_sysname)
+                (void) sd_device_get_sysname(device, &name);
+        if (!name)
+                return log_device_debug_errno(device, SYNTHETIC_ERRNO(ENODATA),
+                                              "No stable identifying information found");
+
+        log_device_debug(device, "Using \"%s\" as stable identifying information", name);
+        l = strlen(name);
+        sz = sizeof(sd_id128_t) + l;
+        v = newa(uint8_t, sz);
+
+        /* Fetch some persistent data unique to this machine */
+        r = sd_id128_get_machine((sd_id128_t*) v);
+        if (r < 0)
+                 return r;
+        memcpy(v + sizeof(sd_id128_t), name, l);
+
+        /* Let's hash the machine ID plus the device name. We use
+         * a fixed, but originally randomly created hash key here. */
+        *result = htole64(siphash24(v, sz, HASH_KEY.bytes));
+        return 0;
+}
diff --git a/src/libsystemd/sd-network/network-util.h b/src/libsystemd/sd-network/network-util.h
index 1422a57279..2d05b666cb 100644
--- a/src/libsystemd/sd-network/network-util.h
+++ b/src/libsystemd/sd-network/network-util.h
@@ -1,6 +1,9 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 #pragma once
 
+#include <inttypes.h>
+#include <stdbool.h>
+
 #include "sd-device.h"
 #include "sd-network.h"
 
@@ -61,3 +64,5 @@ typedef struct LinkOperationalStateRange {
 int parse_operational_state_range(const char *str, LinkOperationalStateRange *out);
 
 char *link_get_type_string(sd_device *device, unsigned short iftype);
+int net_get_unique_predictable_data(sd_device *device, bool use_sysname, uint64_t *result);
+const char *net_get_name_persistent(sd_device *device);