Prep v240 : Add busctl to be shipped with elogind.

(emersion):
> sd-bus is shipped with elogind, so it makes sense to ship the
> busctl command, too.

This is not only a nice helper tool to take a closer look at what is
happening on the dbus, it will also prove to be usefull if something
like issue #59 happens ever again. There we had to use dbus-send
directly to dissect the bus traffic.

Bug: #86
Closes: #86
Signed-off-by: Sven Eden <sven.eden@prydeworx.com>

2 files changed, 613 insertions, 0 deletions

diff --git a/src/libelogind/sd-bus/bus-dump.c b/src/libelogind/sd-bus/bus-dump.c
new file mode 100644
index 000000000..635403b1e
--- /dev/null
+++ b/src/libelogind/sd-bus/bus-dump.c
@@ -0,0 +1,591 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+/***
+***/
+
+#include "alloc-util.h"
+#include "bus-dump.h"
+#include "bus-internal.h"
+#include "bus-message.h"
+#include "bus-type.h"
+#include "cap-list.h"
+#include "capability-util.h"
+#include "fileio.h"
+#include "format-util.h"
+#include "locale-util.h"
+#include "macro.h"
+#include "string-util.h"
+#include "strv.h"
+#include "terminal-util.h"
+#include "util.h"
+
+static char *indent(unsigned level, unsigned flags) {
+        char *p;
+        unsigned n, i = 0;
+
+        n = 0;
+
+        if (flags & BUS_MESSAGE_DUMP_SUBTREE_ONLY && level > 0)
+                level -= 1;
+
+        if (flags & BUS_MESSAGE_DUMP_WITH_HEADER)
+                n += 2;
+
+        p = new(char, n + level*8 + 1);
+        if (!p)
+                return NULL;
+
+        if (flags & BUS_MESSAGE_DUMP_WITH_HEADER) {
+                p[i++] = ' ';
+                p[i++] = ' ';
+        }
+
+        memset(p + i, ' ', level*8);
+        p[i + level*8] = 0;
+
+        return p;
+}
+
+int bus_message_dump(sd_bus_message *m, FILE *f, unsigned flags) {
+        unsigned level = 1;
+        int r;
+
+        assert(m);
+
+        if (!f)
+                f = stdout;
+
+        if (flags & BUS_MESSAGE_DUMP_WITH_HEADER) {
+                fprintf(f,
+                        "%s%s%s Type=%s%s%s  Endian=%c  Flags=%u  Version=%u  Priority=%"PRIi64,
+                        m->header->type == SD_BUS_MESSAGE_METHOD_ERROR ? ansi_highlight_red() :
+                        m->header->type == SD_BUS_MESSAGE_METHOD_RETURN ? ansi_highlight_green() :
+                        m->header->type != SD_BUS_MESSAGE_SIGNAL ? ansi_highlight() : "", special_glyph(TRIANGULAR_BULLET), ansi_normal(),
+                        ansi_highlight(), bus_message_type_to_string(m->header->type), ansi_normal(),
+                        m->header->endian,
+                        m->header->flags,
+                        m->header->version,
+                        m->priority);
+
+                /* Display synthetic message serial number in a more readable
+                 * format than (uint32_t) -1 */
+                if (BUS_MESSAGE_COOKIE(m) == 0xFFFFFFFFULL)
+                        fprintf(f, " Cookie=-1");
+                else
+                        fprintf(f, " Cookie=%" PRIu64, BUS_MESSAGE_COOKIE(m));
+
+                if (m->reply_cookie != 0)
+                        fprintf(f, "  ReplyCookie=%" PRIu64, m->reply_cookie);
+
+                fputs("\n", f);
+
+                if (m->sender)
+                        fprintf(f, "  Sender=%s%s%s", ansi_highlight(), m->sender, ansi_normal());
+                if (m->destination)
+                        fprintf(f, "  Destination=%s%s%s", ansi_highlight(), m->destination, ansi_normal());
+                if (m->path)
+                        fprintf(f, "  Path=%s%s%s", ansi_highlight(), m->path, ansi_normal());
+                if (m->interface)
+                        fprintf(f, "  Interface=%s%s%s", ansi_highlight(), m->interface, ansi_normal());
+                if (m->member)
+                        fprintf(f, "  Member=%s%s%s", ansi_highlight(), m->member, ansi_normal());
+
+                if (m->sender || m->destination || m->path || m->interface || m->member)
+                        fputs("\n", f);
+
+                if (sd_bus_error_is_set(&m->error))
+                        fprintf(f,
+                                "  ErrorName=%s%s%s"
+                                "  ErrorMessage=%s\"%s\"%s\n",
+                                ansi_highlight_red(), strna(m->error.name), ansi_normal(),
+                                ansi_highlight_red(), strna(m->error.message), ansi_normal());
+
+                if (m->monotonic != 0)
+                        fprintf(f, "  Monotonic="USEC_FMT, m->monotonic);
+                if (m->realtime != 0)
+                        fprintf(f, "  Realtime="USEC_FMT, m->realtime);
+                if (m->seqnum != 0)
+                        fprintf(f, "  SequenceNumber=%"PRIu64, m->seqnum);
+
+                if (m->monotonic != 0 || m->realtime != 0 || m->seqnum != 0)
+                        fputs("\n", f);
+
+                bus_creds_dump(&m->creds, f, true);
+        }
+
+        r = sd_bus_message_rewind(m, !(flags & BUS_MESSAGE_DUMP_SUBTREE_ONLY));
+        if (r < 0)
+                return log_error_errno(r, "Failed to rewind: %m");
+
+        if (!(flags & BUS_MESSAGE_DUMP_SUBTREE_ONLY)) {
+                _cleanup_free_ char *prefix = NULL;
+
+                prefix = indent(0, flags);
+                if (!prefix)
+                        return log_oom();
+
+                fprintf(f, "%sMESSAGE \"%s\" {\n", prefix, strempty(m->root_container.signature));
+        }
+
+        for (;;) {
+                _cleanup_free_ char *prefix = NULL;
+                const char *contents = NULL;
+                char type;
+                union {
+                        uint8_t u8;
+                        uint16_t u16;
+                        int16_t s16;
+                        uint32_t u32;
+                        int32_t s32;
+                        uint64_t u64;
+                        int64_t s64;
+                        double d64;
+                        const char *string;
+                        int i;
+                } basic;
+
+                r = sd_bus_message_peek_type(m, &type, &contents);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to peek type: %m");
+
+                if (r == 0) {
+                        if (level <= 1)
+                                break;
+
+                        r = sd_bus_message_exit_container(m);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to exit container: %m");
+
+                        level--;
+
+                        prefix = indent(level, flags);
+                        if (!prefix)
+                                return log_oom();
+
+                        fprintf(f, "%s};\n", prefix);
+                        continue;
+                }
+
+                prefix = indent(level, flags);
+                if (!prefix)
+                        return log_oom();
+
+                if (bus_type_is_container(type) > 0) {
+                        r = sd_bus_message_enter_container(m, type, contents);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to enter container: %m");
+
+                        if (type == SD_BUS_TYPE_ARRAY)
+                                fprintf(f, "%sARRAY \"%s\" {\n", prefix, contents);
+                        else if (type == SD_BUS_TYPE_VARIANT)
+                                fprintf(f, "%sVARIANT \"%s\" {\n", prefix, contents);
+                        else if (type == SD_BUS_TYPE_STRUCT)
+                                fprintf(f, "%sSTRUCT \"%s\" {\n", prefix, contents);
+                        else if (type == SD_BUS_TYPE_DICT_ENTRY)
+                                fprintf(f, "%sDICT_ENTRY \"%s\" {\n", prefix, contents);
+
+                        level++;
+
+                        continue;
+                }
+
+                r = sd_bus_message_read_basic(m, type, &basic);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to get basic: %m");
+
+                assert(r > 0);
+
+                switch (type) {
+
+                case SD_BUS_TYPE_BYTE:
+                        fprintf(f, "%sBYTE %s%u%s;\n", prefix, ansi_highlight(), basic.u8, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_BOOLEAN:
+                        fprintf(f, "%sBOOLEAN %s%s%s;\n", prefix, ansi_highlight(), true_false(basic.i), ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_INT16:
+                        fprintf(f, "%sINT16 %s%i%s;\n", prefix, ansi_highlight(), basic.s16, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_UINT16:
+                        fprintf(f, "%sUINT16 %s%u%s;\n", prefix, ansi_highlight(), basic.u16, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_INT32:
+                        fprintf(f, "%sINT32 %s%i%s;\n", prefix, ansi_highlight(), basic.s32, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_UINT32:
+                        fprintf(f, "%sUINT32 %s%u%s;\n", prefix, ansi_highlight(), basic.u32, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_INT64:
+                        fprintf(f, "%sINT64 %s%"PRIi64"%s;\n", prefix, ansi_highlight(), basic.s64, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_UINT64:
+                        fprintf(f, "%sUINT64 %s%"PRIu64"%s;\n", prefix, ansi_highlight(), basic.u64, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_DOUBLE:
+                        fprintf(f, "%sDOUBLE %s%g%s;\n", prefix, ansi_highlight(), basic.d64, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_STRING:
+                        fprintf(f, "%sSTRING \"%s%s%s\";\n", prefix, ansi_highlight(), basic.string, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_OBJECT_PATH:
+                        fprintf(f, "%sOBJECT_PATH \"%s%s%s\";\n", prefix, ansi_highlight(), basic.string, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_SIGNATURE:
+                        fprintf(f, "%sSIGNATURE \"%s%s%s\";\n", prefix, ansi_highlight(), basic.string, ansi_normal());
+                        break;
+
+                case SD_BUS_TYPE_UNIX_FD:
+                        fprintf(f, "%sUNIX_FD %s%i%s;\n", prefix, ansi_highlight(), basic.i, ansi_normal());
+                        break;
+
+                default:
+                        assert_not_reached("Unknown basic type.");
+                }
+        }
+
+        if (!(flags & BUS_MESSAGE_DUMP_SUBTREE_ONLY)) {
+                _cleanup_free_ char *prefix = NULL;
+
+                prefix = indent(0, flags);
+                if (!prefix)
+                        return log_oom();
+
+                fprintf(f, "%s};\n\n", prefix);
+        }
+
+        return 0;
+}
+
+static void dump_capabilities(
+                sd_bus_creds *c,
+                FILE *f,
+                const char *name,
+                bool terse,
+                int (*has)(sd_bus_creds *c, int capability)) {
+
+        unsigned long i, last_cap;
+        unsigned n = 0;
+        int r;
+
+        assert(c);
+        assert(f);
+        assert(name);
+        assert(has);
+
+        i = 0;
+        r = has(c, i);
+        if (r < 0)
+                return;
+
+        fprintf(f, "%s%s=%s", terse ? "  " : "", name, terse ? "" : ansi_highlight());
+        last_cap = cap_last_cap();
+
+        for (;;) {
+                if (r > 0) {
+
+                        if (n > 0)
+                                fputc(' ', f);
+                        if (n % 4 == 3)
+                                fprintf(f, terse ? "\n          " : "\n        ");
+
+                        fprintf(f, "%s", strna(capability_to_name(i)));
+                        n++;
+                }
+
+                i++;
+
+                if (i > last_cap)
+                        break;
+
+                r = has(c, i);
+        }
+
+        fputs("\n", f);
+
+        if (!terse)
+                fputs(ansi_normal(), f);
+}
+
+int bus_creds_dump(sd_bus_creds *c, FILE *f, bool terse) {
+        uid_t owner, audit_loginuid;
+        uint32_t audit_sessionid;
+        char **cmdline = NULL, **well_known = NULL;
+        const char *prefix, *color, *suffix, *s;
+        int r, q, v, w, z;
+
+        assert(c);
+
+        if (!f)
+                f = stdout;
+
+        if (terse) {
+                prefix = "  ";
+                suffix = "";
+                color = "";
+        } else {
+                const char *off;
+
+                prefix = "";
+                color = ansi_highlight();
+
+                off = ansi_normal();
+                suffix = strjoina(off, "\n");
+        }
+
+        if (c->mask & SD_BUS_CREDS_PID)
+                fprintf(f, "%sPID=%s"PID_FMT"%s", prefix, color, c->pid, suffix);
+        if (c->mask & SD_BUS_CREDS_TID)
+                fprintf(f, "%sTID=%s"PID_FMT"%s", prefix, color, c->tid, suffix);
+        if (c->mask & SD_BUS_CREDS_PPID) {
+                if (c->ppid == 0)
+                        fprintf(f, "%sPPID=%sn/a%s", prefix, color, suffix);
+                else
+                        fprintf(f, "%sPPID=%s"PID_FMT"%s", prefix, color, c->ppid, suffix);
+        }
+        if (c->mask & SD_BUS_CREDS_TTY)
+                fprintf(f, "%sTTY=%s%s%s", prefix, color, strna(c->tty), suffix);
+
+        if (terse && ((c->mask & (SD_BUS_CREDS_PID|SD_BUS_CREDS_TID|SD_BUS_CREDS_PPID|SD_BUS_CREDS_TTY))))
+                fputs("\n", f);
+
+        if (c->mask & SD_BUS_CREDS_UID)
+                fprintf(f, "%sUID=%s"UID_FMT"%s", prefix, color, c->uid, suffix);
+        if (c->mask & SD_BUS_CREDS_EUID)
+                fprintf(f, "%sEUID=%s"UID_FMT"%s", prefix, color, c->euid, suffix);
+        if (c->mask & SD_BUS_CREDS_SUID)
+                fprintf(f, "%sSUID=%s"UID_FMT"%s", prefix, color, c->suid, suffix);
+        if (c->mask & SD_BUS_CREDS_FSUID)
+                fprintf(f, "%sFSUID=%s"UID_FMT"%s", prefix, color, c->fsuid, suffix);
+        r = sd_bus_creds_get_owner_uid(c, &owner);
+        if (r >= 0)
+                fprintf(f, "%sOwnerUID=%s"UID_FMT"%s", prefix, color, owner, suffix);
+        if (c->mask & SD_BUS_CREDS_GID)
+                fprintf(f, "%sGID=%s"GID_FMT"%s", prefix, color, c->gid, suffix);
+        if (c->mask & SD_BUS_CREDS_EGID)
+                fprintf(f, "%sEGID=%s"GID_FMT"%s", prefix, color, c->egid, suffix);
+        if (c->mask & SD_BUS_CREDS_SGID)
+                fprintf(f, "%sSGID=%s"GID_FMT"%s", prefix, color, c->sgid, suffix);
+        if (c->mask & SD_BUS_CREDS_FSGID)
+                fprintf(f, "%sFSGID=%s"GID_FMT"%s", prefix, color, c->fsgid, suffix);
+
+        if (c->mask & SD_BUS_CREDS_SUPPLEMENTARY_GIDS) {
+                unsigned i;
+
+                fprintf(f, "%sSupplementaryGIDs=%s", prefix, color);
+                for (i = 0; i < c->n_supplementary_gids; i++)
+                        fprintf(f, "%s" GID_FMT, i > 0 ? " " : "", c->supplementary_gids[i]);
+                fprintf(f, "%s", suffix);
+        }
+
+        if (terse && ((c->mask & (SD_BUS_CREDS_UID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_SUID|SD_BUS_CREDS_FSUID|
+                                  SD_BUS_CREDS_GID|SD_BUS_CREDS_EGID|SD_BUS_CREDS_SGID|SD_BUS_CREDS_FSGID|
+                                  SD_BUS_CREDS_SUPPLEMENTARY_GIDS)) || r >= 0))
+                fputs("\n", f);
+
+        if (c->mask & SD_BUS_CREDS_COMM)
+                fprintf(f, "%sComm=%s%s%s", prefix, color, c->comm, suffix);
+        if (c->mask & SD_BUS_CREDS_TID_COMM)
+                fprintf(f, "%sTIDComm=%s%s%s", prefix, color, c->tid_comm, suffix);
+        if (c->mask & SD_BUS_CREDS_EXE)
+                fprintf(f, "%sExe=%s%s%s", prefix, color, strna(c->exe), suffix);
+
+        if (terse && (c->mask & (SD_BUS_CREDS_EXE|SD_BUS_CREDS_COMM|SD_BUS_CREDS_TID_COMM)))
+                fputs("\n", f);
+
+        r = sd_bus_creds_get_cmdline(c, &cmdline);
+        if (r >= 0) {
+                char **i;
+
+                fprintf(f, "%sCommandLine=%s", prefix, color);
+                STRV_FOREACH(i, cmdline) {
+                        if (i != cmdline)
+                                fputc(' ', f);
+
+                        fputs(*i, f);
+                }
+
+                fprintf(f, "%s", suffix);
+        } else if (r != -ENODATA)
+                fprintf(f, "%sCommandLine=%sn/a%s", prefix, color, suffix);
+
+        if (c->mask & SD_BUS_CREDS_SELINUX_CONTEXT)
+                fprintf(f, "%sLabel=%s%s%s", prefix, color, c->label, suffix);
+        if (c->mask & SD_BUS_CREDS_DESCRIPTION)
+                fprintf(f, "%sDescription=%s%s%s", prefix, color, c->description, suffix);
+
+        if (terse && (c->mask & (SD_BUS_CREDS_SELINUX_CONTEXT|SD_BUS_CREDS_DESCRIPTION)))
+                fputs("\n", f);
+
+        if (c->mask & SD_BUS_CREDS_CGROUP)
+                fprintf(f, "%sCGroup=%s%s%s", prefix, color, c->cgroup, suffix);
+        s = NULL;
+#if 0 /// elogind does not support systemd units
+        r = sd_bus_creds_get_unit(c, &s);
+        if (r != -ENODATA)
+                fprintf(f, "%sUnit=%s%s%s", prefix, color, strna(s), suffix);
+        s = NULL;
+#endif // 0
+        v = sd_bus_creds_get_slice(c, &s);
+        if (v != -ENODATA)
+                fprintf(f, "%sSlice=%s%s%s", prefix, color, strna(s), suffix);
+        s = NULL;
+#if 0 /// elogind does not support systemd units
+        q = sd_bus_creds_get_user_unit(c, &s);
+        if (q != -ENODATA)
+                fprintf(f, "%sUserUnit=%s%s%s", prefix, color, strna(s), suffix);
+        s = NULL;
+#endif // 0
+        w = sd_bus_creds_get_user_slice(c, &s);
+        if (w != -ENODATA)
+                fprintf(f, "%sUserSlice=%s%s%s", prefix, color, strna(s), suffix);
+        s = NULL;
+        z = sd_bus_creds_get_session(c, &s);
+        if (z != -ENODATA)
+                fprintf(f, "%sSession=%s%s%s", prefix, color, strna(s), suffix);
+
+        if (terse && ((c->mask & SD_BUS_CREDS_CGROUP) || r != -ENODATA || q != -ENODATA || v != -ENODATA || w != -ENODATA || z != -ENODATA))
+                fputs("\n", f);
+
+        r = sd_bus_creds_get_audit_login_uid(c, &audit_loginuid);
+        if (r >= 0)
+                fprintf(f, "%sAuditLoginUID=%s"UID_FMT"%s", prefix, color, audit_loginuid, suffix);
+        else if (r != -ENODATA)
+                fprintf(f, "%sAuditLoginUID=%sn/a%s", prefix, color, suffix);
+        q = sd_bus_creds_get_audit_session_id(c, &audit_sessionid);
+        if (q >= 0)
+                fprintf(f, "%sAuditSessionID=%s%"PRIu32"%s", prefix, color, audit_sessionid, suffix);
+        else if (q != -ENODATA)
+                fprintf(f, "%sAuditSessionID=%sn/a%s", prefix, color, suffix);
+
+        if (terse && (r != -ENODATA || q != -ENODATA))
+                fputs("\n", f);
+
+        if (c->mask & SD_BUS_CREDS_UNIQUE_NAME)
+                fprintf(f, "%sUniqueName=%s%s%s", prefix, color, c->unique_name, suffix);
+
+        if (sd_bus_creds_get_well_known_names(c, &well_known) >= 0) {
+                char **i;
+
+                fprintf(f, "%sWellKnownNames=%s", prefix, color);
+                STRV_FOREACH(i, well_known) {
+                        if (i != well_known)
+                                fputc(' ', f);
+
+                        fputs(*i, f);
+                }
+
+                fprintf(f, "%s", suffix);
+        }
+
+        if (terse && (c->mask & SD_BUS_CREDS_UNIQUE_NAME || well_known))
+                fputc('\n', f);
+
+        dump_capabilities(c, f, "EffectiveCapabilities", terse, sd_bus_creds_has_effective_cap);
+        dump_capabilities(c, f, "PermittedCapabilities", terse, sd_bus_creds_has_permitted_cap);
+        dump_capabilities(c, f, "InheritableCapabilities", terse, sd_bus_creds_has_inheritable_cap);
+        dump_capabilities(c, f, "BoundingCapabilities", terse, sd_bus_creds_has_bounding_cap);
+
+        return 0;
+}
+
+/*
+ * For details about the file format, see:
+ *
+ * http://wiki.wireshark.org/Development/LibpcapFileFormat
+ */
+
+typedef struct _packed_ pcap_hdr_s {
+        uint32_t magic_number;   /* magic number */
+        uint16_t version_major;  /* major version number */
+        uint16_t version_minor;  /* minor version number */
+        int32_t  thiszone;       /* GMT to local correction */
+        uint32_t sigfigs;        /* accuracy of timestamps */
+        uint32_t snaplen;        /* max length of captured packets, in octets */
+        uint32_t network;        /* data link type */
+} pcap_hdr_t ;
+
+typedef struct  _packed_ pcaprec_hdr_s {
+        uint32_t ts_sec;         /* timestamp seconds */
+        uint32_t ts_usec;        /* timestamp microseconds */
+        uint32_t incl_len;       /* number of octets of packet saved in file */
+        uint32_t orig_len;       /* actual length of packet */
+} pcaprec_hdr_t;
+
+int bus_pcap_header(size_t snaplen, FILE *f) {
+
+        pcap_hdr_t hdr = {
+                .magic_number = 0xa1b2c3d4U,
+                .version_major = 2,
+                .version_minor = 4,
+                .thiszone = 0, /* UTC */
+                .sigfigs = 0,
+                .network = 231, /* D-Bus */
+        };
+
+        if (!f)
+                f = stdout;
+
+        assert(snaplen > 0);
+        assert((size_t) (uint32_t) snaplen == snaplen);
+
+        hdr.snaplen = (uint32_t) snaplen;
+
+        fwrite(&hdr, 1, sizeof(hdr), f);
+
+        return fflush_and_check(f);
+}
+
+int bus_message_pcap_frame(sd_bus_message *m, size_t snaplen, FILE *f) {
+        struct bus_body_part *part;
+        pcaprec_hdr_t hdr = {};
+        struct timeval tv;
+        unsigned i;
+        size_t w;
+
+        if (!f)
+                f = stdout;
+
+        assert(m);
+        assert(snaplen > 0);
+        assert((size_t) (uint32_t) snaplen == snaplen);
+
+        if (m->realtime != 0)
+                timeval_store(&tv, m->realtime);
+        else
+                assert_se(gettimeofday(&tv, NULL) >= 0);
+
+        hdr.ts_sec = tv.tv_sec;
+        hdr.ts_usec = tv.tv_usec;
+        hdr.orig_len = BUS_MESSAGE_SIZE(m);
+        hdr.incl_len = MIN(hdr.orig_len, snaplen);
+
+        /* write the pcap header */
+        fwrite(&hdr, 1, sizeof(hdr), f);
+
+        /* write the dbus header */
+        w = MIN(BUS_MESSAGE_BODY_BEGIN(m), snaplen);
+        fwrite(m->header, 1, w, f);
+        snaplen -= w;
+
+        /* write the dbus body */
+        MESSAGE_FOREACH_PART(part, i, m) {
+                if (snaplen <= 0)
+                        break;
+
+                w = MIN(part->size, snaplen);
+                fwrite(part->data, 1, w, f);
+                snaplen -= w;
+        }
+
+        return fflush_and_check(f);
+}
diff --git a/src/libelogind/sd-bus/bus-dump.h b/src/libelogind/sd-bus/bus-dump.h
new file mode 100644
index 000000000..8e47411a4
--- /dev/null
+++ b/src/libelogind/sd-bus/bus-dump.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+/***
+***/
+
+#include <stdbool.h>
+#include <stdio.h>
+
+#include "sd-bus.h"
+
+enum {
+        BUS_MESSAGE_DUMP_WITH_HEADER = 1,
+        BUS_MESSAGE_DUMP_SUBTREE_ONLY = 2,
+};
+
+int bus_message_dump(sd_bus_message *m, FILE *f, unsigned flags);
+
+int bus_creds_dump(sd_bus_creds *c, FILE *f, bool terse);
+
+int bus_pcap_header(size_t snaplen, FILE *f);
+int bus_message_pcap_frame(sd_bus_message *m, size_t snaplen, FILE *f);