[PATCH iproute 1/2] json_writer: support control character escaping

[PATCH iproute 1/2] json_writer: support control character escaping

[Stephen Hemminger]

Iproute2 never handled control characters in strings correctly.
There are some cases like where string is under user control
like paths in ss command. Make iproute2 json output conform
to RFC 8259.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/json_writer.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/json_writer.c b/lib/json_writer.c
index 2f3936c2..7202621e 100644
--- a/lib/json_writer.c
+++ b/lib/json_writer.c
@@ -53,7 +53,7 @@ static void jsonw_eor(json_writer_t *self)
 
 
 /* Output JSON encoded string */
-/* Handles C escapes, does not do Unicode */
+/* Handles C escapes and control characters per RFC 8259 */
 static void jsonw_puts(json_writer_t *self, const char *str)
 {
 	putc('"', self->out);
@@ -81,7 +81,10 @@ static void jsonw_puts(json_writer_t *self, const char *str)
 			fputs("\\\"", self->out);
 			break;
 		default:
-			putc(*str, self->out);
+			if ((unsigned char)*str < 0x20 || *str == 0x7f)
+				fprintf(self->out, "\\u%04x", *str);
+			else
+				putc(*str, self->out);
 		}
 	putc('"', self->out);
 }
-- 
2.53.0

[PATCH iproute 2/2] json_writer: fix builtin test code

[Stephen Hemminger]

The code under #ifdef was not generating valid JSON
and it is missing test for control characters.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/json_writer.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/lib/json_writer.c b/lib/json_writer.c
index 7202621e..d4a1c72b 100644
--- a/lib/json_writer.c
+++ b/lib/json_writer.c
@@ -369,7 +369,7 @@ int main(int argc, char **argv)
 	jsonw_null_field(wr, "my_null");
 
 	jsonw_name(wr, "special chars");
-	jsonw_start_array(wr);
+	jsonw_start_object(wr);
 	jsonw_string_field(wr, "slash", "/");
 	jsonw_string_field(wr, "newline", "\n");
 	jsonw_string_field(wr, "tab", "\t");
@@ -377,7 +377,14 @@ int main(int argc, char **argv)
 	jsonw_string_field(wr, "quote", "\"");
 	jsonw_string_field(wr, "tick", "\'");
 	jsonw_string_field(wr, "backslash", "\\");
-	jsonw_end_array(wr);
+	jsonw_end_object(wr);
+
+	jsonw_name(wr, "control chars");
+	jsonw_start_object(wr);
+	jsonw_string_field(wr, "bell", "\a");
+	jsonw_string_field(wr, "esc", "\033");
+	jsonw_string_field(wr, "del", "\177");
+	jsonw_end_object(wr);
 
 	jsonw_end_object(wr);
 
-- 
2.53.0

Re: [PATCH iproute 1/2] json_writer: support control character escaping

[patchwork-bot+netdevbpf]

Hello:

This series was applied to iproute2/iproute2.git (main)
by Stephen Hemminger <stephen@networkplumber.org>:

On Fri, 10 Apr 2026 15:47:44 -0700 you wrote:
> Iproute2 never handled control characters in strings correctly.
> There are some cases like where string is under user control
> like paths in ss command. Make iproute2 json output conform
> to RFC 8259.
> 
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> 
> [...]

Here is the summary with links:
  - [iproute,1/2] json_writer: support control character escaping
    https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/commit/?id=9e99260759b7
  - [iproute,2/2] json_writer: fix builtin test code
    https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/commit/?id=fe811be6564c

You are awesome, thank you!
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