systemd: move basic systemd library to shared/nm-utils

For better or worse, we already pull in large parts of systemd sources.

I need a base64 decode implementation (because glib's g_base64_decode()
cannot reject invalid encodings). Instead of coming up with my own or
copy-paste if from somewhere, reuse systemd's unbase64mem().

But for that, make systemd's basic bits an independent static library
first because I will need it in libnm-core.

This doesn't really change anything except making "libnm-systemd-core.la"
an indpendent static library that could be used from "libnm-core". We
shall still be mindful about which internal code of systemd we use, and only
access functionality that is exposed via "systemd/nm-sd-utils-shared.h".

shared/systemd/src/basic/ether-addr-util.c

@@ -0,0 +1,113 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include "nm-sd-adapt-shared.h"
+
+#include <errno.h>
+#include <net/ethernet.h>
+#include <stdio.h>
+#include <sys/types.h>
+
+#include "ether-addr-util.h"
+#include "macro.h"
+#include "string-util.h"
+
+char* ether_addr_to_string(const struct ether_addr *addr, char buffer[ETHER_ADDR_TO_STRING_MAX]) {
+        assert(addr);
+        assert(buffer);
+
+        /* Like ether_ntoa() but uses %02x instead of %x to print
+         * ethernet addresses, which makes them look less funny. Also,
+         * doesn't use a static buffer. */
+
+        sprintf(buffer, "%02x:%02x:%02x:%02x:%02x:%02x",
+                addr->ether_addr_octet[0],
+                addr->ether_addr_octet[1],
+                addr->ether_addr_octet[2],
+                addr->ether_addr_octet[3],
+                addr->ether_addr_octet[4],
+                addr->ether_addr_octet[5]);
+
+        return buffer;
+}
+
+int ether_addr_compare(const struct ether_addr *a, const struct ether_addr *b) {
+        return memcmp(a, b, ETH_ALEN);
+}
+
+static void ether_addr_hash_func(const struct ether_addr *p, struct siphash *state) {
+        siphash24_compress(p, sizeof(struct ether_addr), state);
+}
+
+DEFINE_HASH_OPS(ether_addr_hash_ops, struct ether_addr, ether_addr_hash_func, ether_addr_compare);
+
+int ether_addr_from_string(const char *s, struct ether_addr *ret) {
+        size_t pos = 0, n, field;
+        char sep = '\0';
+        const char *hex = HEXDIGITS, *hexoff;
+        size_t x;
+        bool touched;
+
+#define parse_fields(v)                                         \
+        for (field = 0; field < ELEMENTSOF(v); field++) {       \
+                touched = false;                                \
+                for (n = 0; n < (2 * sizeof(v[0])); n++) {      \
+                        if (s[pos] == '\0')                     \
+                                break;                          \
+                        hexoff = strchr(hex, s[pos]);           \
+                        if (!hexoff)                            \
+                                break;                          \
+                        assert(hexoff >= hex);                  \
+                        x = hexoff - hex;                       \
+                        if (x >= 16)                            \
+                                x -= 6; /* A-F */               \
+                        assert(x < 16);                         \
+                        touched = true;                         \
+                        v[field] <<= 4;                         \
+                        v[field] += x;                          \
+                        pos++;                                  \
+                }                                               \
+                if (!touched)                                   \
+                        return -EINVAL;                         \
+                if (field < (ELEMENTSOF(v)-1)) {                \
+                        if (s[pos] != sep)                      \
+                                return -EINVAL;                 \
+                        else                                    \
+                                pos++;                          \
+                }                                               \
+        }
+
+        assert(s);
+        assert(ret);
+
+        s += strspn(s, WHITESPACE);
+        sep = s[strspn(s, hex)];
+
+        if (sep == '.') {
+                uint16_t shorts[3] = { 0 };
+
+                parse_fields(shorts);
+
+                if (s[pos] != '\0')
+                        return -EINVAL;
+
+                for (n = 0; n < ELEMENTSOF(shorts); n++) {
+                        ret->ether_addr_octet[2*n] = ((shorts[n] & (uint16_t)0xff00) >> 8);
+                        ret->ether_addr_octet[2*n + 1] = (shorts[n] & (uint16_t)0x00ff);
+                }
+
+        } else if (IN_SET(sep, ':', '-')) {
+                struct ether_addr out = ETHER_ADDR_NULL;
+
+                parse_fields(out.ether_addr_octet);
+
+                if (s[pos] != '\0')
+                        return -EINVAL;
+
+                for (n = 0; n < ELEMENTSOF(out.ether_addr_octet); n++)
+                        ret->ether_addr_octet[n] = out.ether_addr_octet[n];
+
+        } else
+                return -EINVAL;
+
+        return 0;
+}