dhcp-message-dump: introduce dump_dhcp_message()

It dumps DHCP messages in a human friendly format.
It will be used in networkctl in a later commit.

src/libsystemd-network/dhcp-message-dump.h

@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "dhcp-message.h"
+
+typedef enum {
+        DUMP_DHCP_MESSAGE_LEGEND = 1 << 0,
+        DUMP_DHCP_MESSAGE_FULL   = 1 << 1,
+} DumpDHCPMessageFlag;
+
+int dump_dhcp_message(sd_dhcp_message *message, char * const *args, DumpDHCPMessageFlag flags);

src/libsystemd-network/meson.build

@@ -4,6 +4,7 @@ libsystemd_network_sources = files(
         'arp-util.c',
         'dhcp-client-send.c',
         'dhcp-message.c',
+        'dhcp-message-dump.c',
         'dhcp-network.c',
         'dhcp-option.c',
         'dhcp-packet.c',

src/libsystemd-network/test-dhcp-message.c

@@ -7,6 +7,7 @@
 #include "alloc-util.h"
 #include "dhcp-client-id-internal.h"
 #include "dhcp-message.h"
+#include "dhcp-message-dump.h"
 #include "dhcp-protocol.h"
 #include "dhcp-route.h"
 #include "dns-packet.h"
@@ -545,6 +546,9 @@ TEST(dhcp_message) {
         /* send */
         verify_send_udp(m, xid, &hw_addr);
         verify_send_raw(m, xid, &hw_addr);
+
+        /* dump */
+        ASSERT_OK(dump_dhcp_message(m, /* args= */ NULL, DUMP_DHCP_MESSAGE_LEGEND | DUMP_DHCP_MESSAGE_FULL));
 }
 
 static void test_domains_one(size_t len, const uint8_t *data, char * const *expected) {
@@ -581,6 +585,8 @@ static void test_domains_one(size_t len, const uint8_t *data, char * const *expe
         ASSERT_OK(dhcp_message_append_option(m, SD_DHCP_OPTION_SIP_SERVER, len + 1 - (len + 1) / 2, sip + (len + 1) / 2));
         ASSERT_OK(dhcp_message_get_option_domains(m, SD_DHCP_OPTION_SIP_SERVER, &strv));
         ASSERT_TRUE(strv_equal(strv, expected));
+
+        ASSERT_OK(dump_dhcp_message(m, STRV_MAKE("119", "120"), DUMP_DHCP_MESSAGE_LEGEND | DUMP_DHCP_MESSAGE_FULL));
 }
 
 static void test_domains_fail(size_t len, const uint8_t *data) {
@@ -804,6 +810,8 @@ TEST(dnr) {
         ASSERT_EQ(resolvers[1].port, 33u);
         ASSERT_NULL(resolvers[1].dohpath);
 
+        ASSERT_OK(dump_dhcp_message(m, STRV_MAKE("162"), DUMP_DHCP_MESSAGE_LEGEND | DUMP_DHCP_MESSAGE_FULL));
+
         /* missing DoH path */
         static uint8_t invalid[] = {
                 /* length */
@@ -875,4 +883,60 @@ TEST(dnr) {
         ASSERT_ERROR(dhcp_message_get_option_dnr(m, NULL, NULL), EMSGSIZE);
 }
 
+TEST(dump_vendor) {
+        _cleanup_(sd_dhcp_message_unrefp) sd_dhcp_message *m = NULL;
+        ASSERT_OK(dhcp_message_new(&m));
+
+        /* Vendor Specific Information (43) -- TLV */
+        static uint8_t option_43[] = {
+                1, 6, 'm', 'o', 'd', 'e', 'm', '1',
+                2, 6, 's', 't', 'a', 't', 'u', 's',
+                3, 6, 1, 2, 3, 4, 5, 6,
+        };
+
+        /* Vendor Class Identifier (60) -- typically string */
+        static uint8_t option_60[] = {
+                'n', 'e', 't', 'w', 'o', 'r', 'k', 'd',
+        };
+
+        /* User Class (77) -- length-prefixed data, typically strings */
+        static uint8_t option_77[] = {
+                6, 'l', 'a', 'p', 't', 'o', 'p',
+                4, 'c', 'o', 'r', 'p',
+        };
+
+        /* Vendor-Identifying Vendor Class -- length-prefixed data tagged with enterprise number */
+        static uint8_t option_124[] = {
+                0x00, 0x00, 0x00, 0x09, /* enterprise number: 9 */
+                13,
+                5, 'c', 'i', 's', 'c', 'o',
+                6, 'f', 'o', 'o', 'b', 'a', 'r',
+                0x00, 0x00, 0x11, 0x8b, /* enterprise number: 4491 */
+                21,
+                9,  'd', 'o', 'c', 's', 'i', 's', '3', '.', '0',
+                10, 'e', 'R', 'o', 'u', 't', 'e', 'r', '1', '.', '0',
+        };
+
+        /* Vendor-Identifying Vendor-Specific Information (125) -- sub TLVs with enterprise number */
+        static uint8_t option_125[] = {
+                0x00, 0x00, 0x00, 0x09, /* enterprise number: 9 */
+                12,
+                1, 4, 'C', 'i', 's', 'c',
+                2, 4, 'I', 'O', 'S', 'X',
+                0x00, 0x00, 0x11, 0x8b, /* enterprise number: 4491 */
+                16,
+                1, 6, 'm', 'o', 'd', 'e', 'm', '1',
+                2, 6, 's', 't', 'a', 't', 'u', 's',
+        };
+
+        ASSERT_OK(dhcp_message_append_option(m, 43, ELEMENTSOF(option_43), option_43));
+        ASSERT_OK(dhcp_message_append_option(m, 60, ELEMENTSOF(option_60), option_60));
+        ASSERT_OK(dhcp_message_append_option(m, 77, ELEMENTSOF(option_77), option_77));
+        ASSERT_OK(dhcp_message_append_option(m, 124, ELEMENTSOF(option_124), option_124));
+        ASSERT_OK(dhcp_message_append_option(m, 125, ELEMENTSOF(option_125), option_125));
+
+        ASSERT_OK(dump_dhcp_message(m, STRV_MAKE("43", "60", "77", "124", "125"),
+                                    DUMP_DHCP_MESSAGE_LEGEND | DUMP_DHCP_MESSAGE_FULL));
+}
+
 DEFINE_TEST_MAIN(LOG_DEBUG);