ccan: Update vendored ccan to commit 7c38521d, which includes rustyrussell/ccan#128 and rustyrussell/ccan#130

[nGoline]

On macOS, failed connect() calls return POLLHUP|POLLERR or POLLOUT|POLLHUPfrom poll, and the socket error is set to ECONNREFUSED. Previously ccan's io_poll hardcoded EBADF in the POLLHUP case, causing misleading Bad file descriptor errors. The fix reads SO_ERROR from the socket to surface the real errno.

Also fixes update-ccan Makefile target:

• Use git rev-parse --short HEAD instead of git describe (ccan has no tags)
• Remove reference to ccodearchive.net following rustyrussell/ccan@efd4838

Closes #9236.

The test-level fix for test_networkevents (PR #9140) is still needed but will require a different approach now that the underlying error is correct.

Changelog-None

[ddustin]

Hm something weird happened here. This was changed with #9098 in commit 6664d34, but ccan wasn't updated.

Looks like it was a useful check but not critical.

@sangbida did this solve a particular issue you saw? If so let's get this fixed upstream in ccan so we stay in sync with it.

[sangbida]

I remember it being related to this previous commit here 400f97d. Rusty used json_out_addstrn instead of json_add_str_fmt(result, fieldname, "%.*s", (int)value_len, value);
for better efficiency but injson_out_addstrnthe escape path wasn't using the length that was passed in. The old path did json_add_str_fmt("%.*s", len, ...) + json_escape_len, so escaping respected the explicit length. json_out_addstrn's escape branch instead called json_escape(NULL, str), which uses strlen.

That broke getlog becuase log messages live in a ring buffer and are not NUL-terminated at loglen, so the json_add_stringn(info->response, "log", log, loglen) call in lightningd/log.c hands json_out_addstrn a non-terminated string. When a log line contains an escapable character, strlen reads past loglen into adjacent ring-buffer memory and emits invalid UTF-8.

[sangbida]

I've created a PR to add this into the ccan repo: rustyrussell/ccan#130

Thanks for catching that @ddustin @nGoline!

[nGoline]

Done! Updated ccan to the latest version containing your commit @sangbida.

Are we good to merge @ddustin?