journal-file: lazily fill in machine ID into journal header, if needed

Previously, if we ran in an environment where /etc/machine-id was
not defined, we'd never bother to write it ever again. So it would stay
at all zeroes till the end of times.

Let's make this more robust: whenever we try to append an entry, let's
try to refresh it from the status quo if not initialized yet. Moreover,
when copying records from a different journal file, let's propagate the
machine ID from there.

This should make things more robust and systematic, and match how we
propagate the boot ID and the seqnum ID to some level.

diff --git a/src/libsystemd/sd-journal/journal-file.c b/src/libsystemd/sd-journal/journal-file.c
index 7300ed07810205a10f22b653439898fd135229f3..3e721ef937dff3487979f15cb41645cd152aad5c 100644 (file)
--- a/src/libsystemd/sd-journal/journal-file.c
+++ b/src/libsystemd/sd-journal/journal-file.c
@@ -2087,6 +2087,7 @@ static int journal_file_append_entry_internal(
                 JournalFile *f,
                 const dual_timestamp *ts,
                 const sd_id128_t *boot_id,
+                const sd_id128_t *machine_id,
                 uint64_t xor_hash,
                 const EntryItem items[],
                 size_t n_items,
@@ -2152,6 +2153,10 @@ static int journal_file_append_entry_internal(
                 }
         }
 
+        if (machine_id && sd_id128_is_null(f->header->machine_id))
+                /* Initialize machine ID when not set yet */
+                f->header->machine_id = *machine_id;
+
         osize = offsetof(Object, entry.items) + (n_items * journal_file_entry_item_size(f));
 
         r = journal_file_append_object(f, OBJECT_ENTRY, osize, &o, &np);
@@ -2311,7 +2316,7 @@ int journal_file_append_entry(
         EntryItem *items;
         uint64_t xor_hash = 0;
         struct dual_timestamp _ts;
-        sd_id128_t _boot_id;
+        sd_id128_t _boot_id, _machine_id, *machine_id;
         int r;
 
         assert(f);
@@ -2341,6 +2346,16 @@ int journal_file_append_entry(
                 boot_id = &_boot_id;
         }
 
+        r = sd_id128_get_machine(&_machine_id);
+        if (r < 0) {
+                if (!ERRNO_IS_MACHINE_ID_UNSET(r))
+                        return r;
+
+                /* If the machine ID is not initialized yet, handle gracefully */
+                machine_id = NULL;
+        } else
+                machine_id = &_machine_id;
+
 #if HAVE_GCRYPT
         r = journal_file_maybe_append_tag(f, ts->realtime);
         if (r < 0)
@@ -2390,7 +2405,18 @@ int journal_file_append_entry(
         typesafe_qsort(items, n_iovec, entry_item_cmp);
         n_iovec = remove_duplicate_entry_items(items, n_iovec);
 
-        r = journal_file_append_entry_internal(f, ts, boot_id, xor_hash, items, n_iovec, seqnum, seqnum_id, ret_object, ret_offset);
+        r = journal_file_append_entry_internal(
+                        f,
+                        ts,
+                        boot_id,
+                        machine_id,
+                        xor_hash,
+                        items,
+                        n_iovec,
+                        seqnum,
+                        seqnum_id,
+                        ret_object,
+                        ret_offset);
 
         /* If the memory mapping triggered a SIGBUS then we return an
          * IO error and ignore the error code passed down to us, since
@@ -4190,7 +4216,18 @@ int journal_file_copy_entry(
                         return r;
         }
 
-        r = journal_file_append_entry_internal(to, &ts, boot_id, xor_hash, items, n, seqnum, seqnum_id, NULL, NULL);
+        r = journal_file_append_entry_internal(
+                        to,
+                        &ts,
+                        boot_id,
+                        &from->header->machine_id,
+                        xor_hash,
+                        items,
+                        n,
+                        seqnum,
+                        seqnum_id,
+                        /* ret_object= */ NULL,
+                        /* ret_offset= */ NULL);
 
         if (mmap_cache_fd_got_sigbus(to->cache_fd))
                 return -EIO;