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From 32244f8d21a3e06f6519c47234289da696f6b151 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Sun, 8 Oct 2017 09:05:59 +0200
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Subject: [PATCH] journald: make maximum size of stream log lines configurable
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 and bump it to 48K (#6838)
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This adds a new setting LineMax= to journald.conf, and sets it by
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default to 48K. When we convert stream-based stdout/stderr logging into
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record-based log entries, read up to the specified amount of bytes
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before forcing a line-break.
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This also makes three related changes:
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- When a NUL byte is read we'll not recognize this as alternative line
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  break, instead of silently dropping everything after it. (see #4863)
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- The reason for a line-break is now encoded in the log record, if it
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  wasn't a plain newline. Specifically, we distuingish "nul",
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  "line-max" and "eof", for line breaks due to NUL byte, due to the
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  maximum line length as configured with LineMax= or due to end of
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  stream. This data is stored in the new implicit _LINE_BREAK= field.
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  It's not synthesized for plain \n line breaks.
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- A randomized 128bit ID is assigned to each log stream.
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With these three changes in place it's (mostly) possible to reconstruct
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the original byte streams from log data, as (most) of the context of
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the conversion from the byte stream to log records is saved now. (So,
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the only bits we still drop are empty lines. Which might be something to
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look into in a future change, and which is outside of the scope of this
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work)
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Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=86465
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See: #4863
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Replaces: #4875
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(cherry picked from commit ec20fe5ffb8a00469bab209fff6c069bb93c6db2)
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Resolves: #1442262
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[msekleta: I had to manually rewrite upstream commit, because git
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did very poor job merging old and new code and identified a lot of merge
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conflicts in a code that was totally unrelated.]
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---
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 man/journald.conf.xml            |  18 +++++
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 man/systemd.journal-fields.xml   |  22 ++++++
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 src/journal/journald-gperf.gperf |   1 +
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 src/journal/journald-server.c    |  68 ++++++++++++++++++
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 src/journal/journald-server.h    |   3 +
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 src/journal/journald-stream.c    | 116 +++++++++++++++++++++++++------
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 src/journal/journald.conf        |   1 +
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 7 files changed, 209 insertions(+), 20 deletions(-)
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diff --git a/man/journald.conf.xml b/man/journald.conf.xml
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index 46a498b67..e2d6a1225 100644
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--- a/man/journald.conf.xml
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+++ b/man/journald.conf.xml
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@@ -354,6 +354,24 @@
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         <filename>/dev/console</filename>.</para></listitem>
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       </varlistentry>
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+      <varlistentry>
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+        <term><varname>LineMax=</varname></term>
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+
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+        <listitem><para>The maximum line length to permit when converting stream logs into record logs. When a systemd
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+        unit's standard output/error are connected to the journal via a stream socket, the data read is split into
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+        individual log records at newline (<literal>\n</literal>, ASCII 10) and NUL characters. If no such delimiter is
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+        read for the specified number of bytes a hard log record boundary is artifically inserted, breaking up overly
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+        long lines into multiple log records. Selecting overly large values increases the possible memory usage of the
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+        Journal daemon for each stream client, as in the worst case the journal daemon needs to buffer the specified
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+        number of bytes in memory before it can flush a new log record to disk. Also note that permitting overly large
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+        line maximum line lengths affects compatibility with traditional log protocols as log records might not fit
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+        anymore into a single <constant>AF_UNIX</constant> or <constant>AF_INET</constant> datagram. Takes a size in
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+        bytes. If the value is suffixed with K, M, G or T, the specified size is parsed as Kilobytes, Megabytes,
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+        Gigabytes, or Terabytes (with the base 1024), respectively. Defaults to 48K, which is relatively large but
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+        still small enough so that log records likely fit into network datagrams along with extra room for
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+        metadata. Note that values below 79 are not accepted and will be bumped to 79.</para></listitem>
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+      </varlistentry>
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+
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     </variablelist>
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   </refsect1>
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diff --git a/man/systemd.journal-fields.xml b/man/systemd.journal-fields.xml
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index 7d6c5c715..a53f8def2 100644
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--- a/man/systemd.journal-fields.xml
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+++ b/man/systemd.journal-fields.xml
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@@ -311,6 +311,28 @@
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           </variablelist>
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         </listitem>
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       </varlistentry>
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+      <varlistentry>
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+        <term><varname>_STREAM_ID=</varname></term>
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+        <listitem>
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+          <para>Only applies to <literal>_TRANSPORT=stream</literal> records: specifies a randomized 128bit ID assigned
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+          to the stream connection when it was first created. This ID is useful to reconstruct individual log streams
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+          from the log records: all log records carrying the same stream ID originate from the same stream.</para>
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+        </listitem>
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+      </varlistentry>
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+      <varlistentry>
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+        <term><varname>_LINE_BREAK=</varname></term>
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+        <listitem>
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+          <para>Only applies to <literal>_TRANSPORT=stream</literal> records: indicates that the log message in the
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+          standard output/error stream was not terminated with a normal newline character (<literal>\n</literal>,
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+          i.e. ASCII 10). Specifically, when set this field is one of <option>nul</option> (in case the line was
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+          terminated by a NUL byte), <option>line-max</option> (in case the maximum log line length was reached, as
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+          configured with <varname>LineMax=</varname> in
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+          <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>) or
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+          <option>eof</option> (if this was the last log record of a stream and the stream ended without a final
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+          newline character). Note that this record is not generated when a normal newline character was used for
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+          marking the log line end.</para>
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+        </listitem>
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+      </varlistentry>
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     </variablelist>
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   </refsect1>
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diff --git a/src/journal/journald-gperf.gperf b/src/journal/journald-gperf.gperf
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index 74554c1c3..73327c10e 100644
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--- a/src/journal/journald-gperf.gperf
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+++ b/src/journal/journald-gperf.gperf
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@@ -40,3 +40,4 @@ Journal.MaxLevelKMsg,       config_parse_log_level,  0, offsetof(Server, max_lev
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 Journal.MaxLevelConsole,    config_parse_log_level,  0, offsetof(Server, max_level_console)
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 Journal.MaxLevelWall,       config_parse_log_level,  0, offsetof(Server, max_level_wall)
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 Journal.SplitMode,          config_parse_split_mode, 0, offsetof(Server, split_mode)
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+Journal.LineMax,            config_parse_line_max,   0, offsetof(Server, line_max)
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\ No newline at end of file
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diff --git a/src/journal/journald-server.c b/src/journal/journald-server.c
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index f6f8c30eb..daeecd519 100644
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--- a/src/journal/journald-server.c
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+++ b/src/journal/journald-server.c
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@@ -67,6 +67,10 @@
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 #define RECHECK_AVAILABLE_SPACE_USEC (30*USEC_PER_SEC)
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+/* Pick a good default that is likely to fit into AF_UNIX and AF_INET SOCK_DGRAM datagrams, and even leaves some room
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++ * for a bit of additional metadata. */
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+#define DEFAULT_LINE_MAX (48*1024)
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+
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 static const char* const storage_table[_STORAGE_MAX] = {
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         [STORAGE_AUTO] = "auto",
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         [STORAGE_VOLATILE] = "volatile",
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@@ -83,9 +87,71 @@ static const char* const split_mode_table[_SPLIT_MAX] = {
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         [SPLIT_NONE] = "none",
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 };
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+
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 DEFINE_STRING_TABLE_LOOKUP(split_mode, SplitMode);
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 DEFINE_CONFIG_PARSE_ENUM(config_parse_split_mode, split_mode, SplitMode, "Failed to parse split mode setting");
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+int config_parse_line_max(
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+                const char* unit,
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+                const char *filename,
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+                unsigned line,
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+                const char *section,
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+                unsigned section_line,
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+                const char *lvalue,
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+                int ltype,
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+                const char *rvalue,
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+                void *data,
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+                void *userdata) {
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+
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+        size_t *sz = data;
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+        int r;
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+
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+        assert(filename);
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+        assert(lvalue);
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+        assert(rvalue);
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+        assert(data);
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+
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+        if (isempty(rvalue))
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+                /* Empty assignment means default */
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+                *sz = DEFAULT_LINE_MAX;
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+        else {
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+                uint64_t v;
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+                off_t u;
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+
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+                r = parse_size(rvalue, 1024, &u);
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+                if (r < 0) {
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+                        log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse LineMax= value, ignoring: %s", rvalue);
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+                        return 0;
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+                }
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+
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+                /* Backport note */
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+                /* Upstream ditched use of off_t however our parse_size implementation still takes off_t*
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+                 * as an argument. Since we compile with -Werror, we have two choices, either disable sign-compare
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+                 * warning or do this casting so we don't have to change rest of the code. I think it is
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+                 * better to do cast here instead of rewriting the code so it deals with off_t instead of
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+                 * uint64_t. Doing conversion off_t -> uint64_t is something that we should think about. */
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+                v = (uint64_t) u;
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+
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+                if (v < 79) {
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+                        /* Why specify 79 here as minimum line length? Simply, because the most common traditional
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+                         * terminal size is 80ch, and it might make sense to break one character before the natural
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+                         * line break would occur on that. */
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+                        log_syntax(unit, LOG_WARNING, filename, line, 0, "LineMax= too small, clamping to 79: %s", rvalue);
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+                        *sz = 79;
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+                } else if (v > (uint64_t) (SSIZE_MAX-1)) {
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+                        /* So, why specify SSIZE_MAX-1 here? Because that's one below the largest size value read()
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+                         * can return, and we need one extra byte for the trailing NUL byte. Of course IRL such large
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+                         * memory allocations will fail anyway, hence this limit is mostly theoretical anyway, as we'll
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+                         * fail much earlier anyway. */
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+                        log_syntax(unit, LOG_WARNING, filename, line, 0, "LineMax= too large, clamping to %" PRIu64 ": %s", (uint64_t) (SSIZE_MAX-1), rvalue);
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+                        *sz = SSIZE_MAX-1;
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+                } else
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+                        *sz = (size_t) v;
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+        }
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+
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+        return 0;
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+}
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+
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 static uint64_t available_space(Server *s, bool verbose) {
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         char ids[33];
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         _cleanup_free_ char *p = NULL;
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@@ -1518,6 +1584,8 @@ int server_init(Server *s) {
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         s->max_level_console = LOG_INFO;
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         s->max_level_wall = LOG_EMERG;
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+        s->line_max = DEFAULT_LINE_MAX;
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+
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         memset(&s->system_metrics, 0xFF, sizeof(s->system_metrics));
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         memset(&s->runtime_metrics, 0xFF, sizeof(s->runtime_metrics));
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diff --git a/src/journal/journald-server.h b/src/journal/journald-server.h
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index 7a456c2d5..b29410778 100644
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--- a/src/journal/journald-server.h
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+++ b/src/journal/journald-server.h
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@@ -143,6 +143,8 @@ typedef struct Server {
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         /* Cached cgroup root, so that we don't have to query that all the time */
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         char *cgroup_root;
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+
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+        size_t line_max;
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 } Server;
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 #define N_IOVEC_META_FIELDS 20
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@@ -157,6 +159,7 @@ void server_driver_message(Server *s, sd_id128_t message_id, const char *format,
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 const struct ConfigPerfItem* journald_gperf_lookup(const char *key, unsigned length);
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 int config_parse_storage(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
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+int config_parse_line_max(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
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 const char *storage_to_string(Storage s) _const_;
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 Storage storage_from_string(const char *s) _pure_;
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diff --git a/src/journal/journald-stream.c b/src/journal/journald-stream.c
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index 15c9110c0..4d6b7ad18 100644
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--- a/src/journal/journald-stream.c
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+++ b/src/journal/journald-stream.c
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@@ -53,6 +53,16 @@ typedef enum StdoutStreamState {
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         STDOUT_STREAM_RUNNING
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 } StdoutStreamState;
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+/* The different types of log record terminators: a real \n was read, a NUL character was read, the maximum line length
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+ * was reached, or the end of the stream was reached */
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+
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+typedef enum LineBreak {
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+        LINE_BREAK_NEWLINE,
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+        LINE_BREAK_NUL,
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+        LINE_BREAK_LINE_MAX,
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+        LINE_BREAK_EOF,
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+} LineBreak;
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+
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 struct StdoutStream {
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         Server *server;
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         StdoutStreamState state;
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@@ -71,14 +81,17 @@ struct StdoutStream {
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         bool fdstore:1;
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-        char buffer[LINE_MAX+1];
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+        char *buffer;
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         size_t length;
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+        size_t allocated;
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         sd_event_source *event_source;
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         char *state_file;
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         LIST_FIELDS(StdoutStream, stdout_stream);
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+
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+        char id_field[sizeof("_STREAM_ID=")-1 + SD_ID128_STRING_MAX];
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 };
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 void stdout_stream_free(StdoutStream *s) {
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@@ -101,6 +114,7 @@ void stdout_stream_free(StdoutStream *s) {
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         free(s->identifier);
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         free(s->unit_id);
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         free(s->state_file);
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+        free(s->buffer);
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         free(s);
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 }
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@@ -151,12 +165,14 @@ static int stdout_stream_save(StdoutStream *s) {
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                 "LEVEL_PREFIX=%i\n"
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                 "FORWARD_TO_SYSLOG=%i\n"
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                 "FORWARD_TO_KMSG=%i\n"
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-                "FORWARD_TO_CONSOLE=%i\n",
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+                "FORWARD_TO_CONSOLE=%i\n"
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+                "STREAM_ID=%s\n",
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                 s->priority,
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                 s->level_prefix,
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                 s->forward_to_syslog,
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                 s->forward_to_kmsg,
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-                s->forward_to_console);
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+                s->forward_to_console,
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+                s->id_field + strlen("_STREAM_ID="));
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         if (!isempty(s->identifier)) {
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                 _cleanup_free_ char *escaped;
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@@ -211,8 +227,8 @@ finish:
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         return r;
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 }
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-static int stdout_stream_log(StdoutStream *s, const char *p) {
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-        struct iovec iovec[N_IOVEC_META_FIELDS + 5];
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+static int stdout_stream_log(StdoutStream *s, const char *p, LineBreak line_break) {
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+        struct iovec iovec[N_IOVEC_META_FIELDS + 7];
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         int priority;
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         char syslog_priority[] = "PRIORITY=\0";
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         char syslog_facility[sizeof("SYSLOG_FACILITY=")-1 + DECIMAL_STR_MAX(int) + 1];
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@@ -245,6 +261,8 @@ static int stdout_stream_log(StdoutStream *s, const char *p) {
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         IOVEC_SET_STRING(iovec[n++], "_TRANSPORT=stdout");
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+        IOVEC_SET_STRING(iovec[n++], s->id_field);
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+
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         syslog_priority[strlen("PRIORITY=")] = '0' + LOG_PRI(priority);
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         IOVEC_SET_STRING(iovec[n++], syslog_priority);
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@@ -259,6 +277,18 @@ static int stdout_stream_log(StdoutStream *s, const char *p) {
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                         IOVEC_SET_STRING(iovec[n++], syslog_identifier);
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         }
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+        if (line_break != LINE_BREAK_NEWLINE) {
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+                const char *c;
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+
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+                /* If this log message was generated due to an uncommon line break then mention this in the log
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+                 * entry */
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+
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+                c =     line_break == LINE_BREAK_NUL ?      "_LINE_BREAK=nul" :
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+                        line_break == LINE_BREAK_LINE_MAX ? "_LINE_BREAK=line-max" :
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+                                                            "_LINE_BREAK=eof";
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+                IOVEC_SET_STRING(iovec[n++], c);
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+        }
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+
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         message = strappend("MESSAGE=", p);
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         if (message)
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                 IOVEC_SET_STRING(iovec[n++], message);
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@@ -268,12 +298,18 @@ static int stdout_stream_log(StdoutStream *s, const char *p) {
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         return 0;
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 }
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-static int stdout_stream_line(StdoutStream *s, char *p) {
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+static int stdout_stream_line(StdoutStream *s, char *p, LineBreak line_break) {
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         int r;
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         assert(s);
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         assert(p);
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+        /* line breaks by NUL, line max length or EOF are not permissible during the negotiation part of the protocol */
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+        if (line_break != LINE_BREAK_NEWLINE && s->state != STDOUT_STREAM_RUNNING) {
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+                log_warning("Control protocol line not properly terminated.");
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+                return -EINVAL;
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+        }
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+
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         p = strstrip(p);
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         switch (s->state) {
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@@ -362,7 +398,7 @@ static int stdout_stream_line(StdoutStream *s, char *p) {
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                 return 0;
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         case STDOUT_STREAM_RUNNING:
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-                return stdout_stream_log(s, p);
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+                return stdout_stream_log(s, p, line_break);
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         }
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         assert_not_reached("Unknown stream state");
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@@ -378,21 +414,32 @@ static int stdout_stream_scan(StdoutStream *s, bool force_flush) {
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         p = s->buffer;
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         remaining = s->length;
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         for (;;) {
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-                char *end;
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+                LineBreak line_break;
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                 size_t skip;
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-                end = memchr(p, '\n', remaining);
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-                if (end)
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-                        skip = end - p + 1;
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-                else if (remaining >= sizeof(s->buffer) - 1) {
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-                        end = p + sizeof(s->buffer) - 1;
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+                char *end1, *end2;
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+
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+                end1 = memchr(p, '\n', remaining);
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+                end2 = memchr(p, 0, end1 ? (size_t) (end1 - p) : remaining);
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+
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+                if (end2) {
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+                        /* We found a NUL terminator */
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+                        skip = end2 - p + 1;
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+                        line_break = LINE_BREAK_NUL;
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+                } else if (end1) {
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+                        /* We found a \n terminator */
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+                        *end1 = 0;
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+                        skip = end1 - p + 1;
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+                        line_break = LINE_BREAK_NEWLINE;
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+                } else if (remaining >= s->server->line_max) {
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+                        /* Force a line break after the maximum line length */
dd65c9
+                        *(p + s->server->line_max) = 0;
dd65c9
                         skip = remaining;
dd65c9
+                        line_break = LINE_BREAK_LINE_MAX;
dd65c9
                 } else
dd65c9
                         break;
dd65c9
 
dd65c9
-                *end = 0;
dd65c9
-
dd65c9
-                r = stdout_stream_line(s, p);
dd65c9
+                r = stdout_stream_line(s, p, line_break);
dd65c9
                 if (r < 0)
dd65c9
                         return r;
dd65c9
 
dd65c9
@@ -402,7 +449,7 @@ static int stdout_stream_scan(StdoutStream *s, bool force_flush) {
dd65c9
 
dd65c9
         if (force_flush && remaining > 0) {
dd65c9
                 p[remaining] = 0;
dd65c9
-                r = stdout_stream_line(s, p);
dd65c9
+                r = stdout_stream_line(s, p, LINE_BREAK_EOF);
dd65c9
                 if (r < 0)
dd65c9
                         return r;
dd65c9
 
dd65c9
@@ -420,6 +467,7 @@ static int stdout_stream_scan(StdoutStream *s, bool force_flush) {
dd65c9
 
dd65c9
 static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
dd65c9
         StdoutStream *s = userdata;
dd65c9
+        size_t limit;
dd65c9
         ssize_t l;
dd65c9
         int r;
dd65c9
 
dd65c9
@@ -430,9 +478,20 @@ static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents,
dd65c9
                 goto terminate;
dd65c9
         }
dd65c9
 
dd65c9
-        l = read(s->fd, s->buffer+s->length, sizeof(s->buffer)-1-s->length);
dd65c9
-        if (l < 0) {
dd65c9
+        /* If the buffer is full already (discounting the extra NUL we need), add room for another 1K */
dd65c9
+        if (s->length + 1 >= s->allocated) {
dd65c9
+                if (!GREEDY_REALLOC(s->buffer, s->allocated, s->length + 1 + 1024)) {
dd65c9
+                        log_oom();
dd65c9
+                        goto terminate;
dd65c9
+                }
dd65c9
+        }
dd65c9
+
dd65c9
+        /* Try to make use of the allocated buffer in full, but never read more than the configured line size. Also,
dd65c9
+         * always leave room for a terminating NUL we might need to add. */
dd65c9
+        limit = MIN(s->allocated - 1, s->server->line_max);
dd65c9
 
dd65c9
+        l = read(s->fd, s->buffer + s->length, limit - s->length);
dd65c9
+        if (l < 0) {
dd65c9
                 if (errno == EAGAIN)
dd65c9
                         return 0;
dd65c9
 
dd65c9
@@ -459,11 +518,16 @@ terminate:
dd65c9
 
dd65c9
 static int stdout_stream_install(Server *s, int fd, StdoutStream **ret) {
dd65c9
         _cleanup_(stdout_stream_freep) StdoutStream *stream = NULL;
dd65c9
+        sd_id128_t id;
dd65c9
         int r;
dd65c9
 
dd65c9
         assert(s);
dd65c9
         assert(fd >= 0);
dd65c9
 
dd65c9
+        r = sd_id128_randomize(&id;;
dd65c9
+        if (r < 0)
dd65c9
+                return log_error_errno(r, "Failed to generate stream ID: %m");
dd65c9
+
dd65c9
         stream = new0(StdoutStream, 1);
dd65c9
         if (!stream)
dd65c9
                 return log_oom();
dd65c9
@@ -471,6 +535,8 @@ static int stdout_stream_install(Server *s, int fd, StdoutStream **ret) {
dd65c9
         stream->fd = -1;
dd65c9
         stream->priority = LOG_INFO;
dd65c9
 
dd65c9
+        xsprintf(stream->id_field, "_STREAM_ID=" SD_ID128_FORMAT_STR, SD_ID128_FORMAT_VAL(id));
dd65c9
+
dd65c9
         r = getpeercred(fd, &stream->ucred);
dd65c9
         if (r < 0)
dd65c9
                 return log_error_errno(r, "Failed to determine peer credentials: %m");
dd65c9
@@ -545,7 +611,8 @@ static int stdout_stream_load(StdoutStream *stream, const char *fname) {
dd65c9
                 *level_prefix = NULL,
dd65c9
                 *forward_to_syslog = NULL,
dd65c9
                 *forward_to_kmsg = NULL,
dd65c9
-                *forward_to_console = NULL;
dd65c9
+                *forward_to_console = NULL,
dd65c9
+                *stream_id = NULL;
dd65c9
         int r;
dd65c9
 
dd65c9
         assert(stream);
dd65c9
@@ -565,6 +632,7 @@ static int stdout_stream_load(StdoutStream *stream, const char *fname) {
dd65c9
                            "FORWARD_TO_CONSOLE", &forward_to_console,
dd65c9
                            "IDENTIFIER", &stream->identifier,
dd65c9
                            "UNIT", &stream->unit_id,
dd65c9
+                           "STREAM_ID", &stream_id,
dd65c9
                            NULL);
dd65c9
         if (r < 0)
dd65c9
                 return log_error_errno(r, "Failed to read: %s", stream->state_file);
dd65c9
@@ -601,6 +669,14 @@ static int stdout_stream_load(StdoutStream *stream, const char *fname) {
dd65c9
                         stream->forward_to_console = r;
dd65c9
         }
dd65c9
 
dd65c9
+        if (stream_id) {
dd65c9
+                sd_id128_t id;
dd65c9
+
dd65c9
+                r = sd_id128_from_string(stream_id, &id;;
dd65c9
+                if (r >= 0)
dd65c9
+                        xsprintf(stream->id_field, "_STREAM_ID=" SD_ID128_FORMAT_STR, SD_ID128_FORMAT_VAL(id));
dd65c9
+        }
dd65c9
+
dd65c9
         return 0;
dd65c9
 }
dd65c9
 
dd65c9
diff --git a/src/journal/journald.conf b/src/journal/journald.conf
dd65c9
index 3907dfb7f..5355ec2b2 100644
dd65c9
--- a/src/journal/journald.conf
dd65c9
+++ b/src/journal/journald.conf
dd65c9
@@ -37,3 +37,4 @@
dd65c9
 #MaxLevelKMsg=notice
dd65c9
 #MaxLevelConsole=info
dd65c9
 #MaxLevelWall=emerg
dd65c9
+#LineMax=48K