commit f5e7753b9e82ade7e401ad8adce103855b2fad29
author Piotr Dymacz <pepe2k@gmail.com> Sun Oct 30 17:43:45 2022 +0100
committer Dominik Ermel <56024351+de-nordic@users.noreply.github.com> Tue Mar 21 15:10:12 2023 +0100
tree 57b7ef34107da0c7f449274122eb6805e06c6916
parent 569b1d6393dde711be971b2db54f628a85d81901

boot_serial: support fragmentation for outgoing SMP packets

The mcumgr packet sent over serial should be fragmented into frames of
up to 127 bytes, including 2-bytes frame start header and 1-byte for
terminating newline [1], resulting in up to 124 bytes for the base64
encoded payload.

Current implementation doesn't fulfill above requirement and transmits
single frames, without considering their length. This change introduces
support for fragmenting as defined in 'SMP over console' specification.

[1] github.com/apache/mynewt-mcumgr/blob/master/transport/smp-console.md

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>

boot/boot_serial/src/boot_serial.c

diff --git a/boot/boot_serial/src/boot_serial.c b/boot/boot_serial/src/boot_serial.c
index e346280..c9a9a37 100644
--- a/boot/boot_serial/src/boot_serial.c
+++ b/boot/boot_serial/src/boot_serial.c
@@ -83,6 +83,7 @@
 #endif
 
 #define BOOT_SERIAL_OUT_MAX     (128 * BOOT_IMAGE_NUMBER)
+#define BOOT_SERIAL_FRAME_MTU   124 /* 127 - pkt start (2 bytes) and stop (1 byte) */
 
 #ifdef __ZEPHYR__
 /* base64 lib encodes data to null-terminated string */
@@ -758,9 +759,10 @@
 boot_serial_output(void)
 {
     char *data;
-    int len;
+    int len, out;
     uint16_t crc;
     uint16_t totlen;
+    char pkt_cont[2] = { SHELL_NLIP_DATA_START1, SHELL_NLIP_DATA_START2 };
     char pkt_start[2] = { SHELL_NLIP_PKT_START1, SHELL_NLIP_PKT_START2 };
     char buf[BOOT_SERIAL_OUT_MAX + sizeof(*bs_hdr) + sizeof(crc) + sizeof(totlen)];
     char encoded_buf[BASE64_ENCODE_SIZE(sizeof(buf))];
@@ -786,8 +788,6 @@
 #endif
     crc = htons(crc);
 
-    boot_uf->write(pkt_start, sizeof(pkt_start));
-
     totlen = len + sizeof(*bs_hdr) + sizeof(crc);
     totlen = htons(totlen);
 
@@ -810,8 +810,23 @@
 #else
     totlen = base64_encode(buf, totlen, encoded_buf, 1);
 #endif
-    boot_uf->write(encoded_buf, totlen);
-    boot_uf->write("\n", 1);
+
+    out = 0;
+    while (out < totlen) {
+        if (out == 0) {
+            boot_uf->write(pkt_start, sizeof(pkt_start));
+        } else {
+            boot_uf->write(pkt_cont, sizeof(pkt_cont));
+        }
+
+        len = MIN(BOOT_SERIAL_FRAME_MTU, totlen - out);
+        boot_uf->write(&encoded_buf[out], len);
+
+        out += len;
+
+        boot_uf->write("\n", 1);
+    }
+
     BOOT_LOG_INF("TX");
 }