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fix(modem): Fix autodetect to support ACFC mode in PPP frames

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Closes https://github.com/espressif/esp-protocols/issues/801
This commit is contained in:
David Cermak
2025-04-15 17:14:57 +02:00
parent 01952f21cb
commit 8b328a6904
2 changed files with 41 additions and 16 deletions
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56
components/esp_modem/src/esp_modem_dce.cpp
View File

@ -1,5 +1,5 @@
/*
* SPDX-FileCopyrightText: 2021-2024 Espressif Systems (Shanghai) CO LTD
* SPDX-FileCopyrightText: 2021-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
@ -283,6 +283,10 @@ namespace ppp {
// Test that we're in the PPP mode by sending an LCP protocol echo request and expecting LCP echo reply
constexpr std::array<uint8_t, 16> lcp_echo_request = {0x7e, 0xff, 0x03, 0xc0, 0x21, 0x09, 0x01, 0x00, 0x08, 0x99, 0xd1, 0x35, 0xc1, 0x8e, 0x2c, 0x7e };
constexpr std::array<uint8_t, 5> lcp_echo_reply_head = {0x7e, 0xff, 0x7d, 0x23, 0xc0};
// PPP frame delimiter
constexpr uint8_t ppp_delimiter = 0x7e;
// LCP protocol ID
constexpr std::array<uint8_t, 2> lcp_protocol_id = {0xc0, 0x21};
const size_t mode = 1 << 0;
const int timeout = 200;
}
@ -325,27 +329,48 @@ modem_mode DCE_Mode::guess_unsafe(DTE *dte, bool with_cmux)
ESP_LOG_BUFFER_HEXDUMP("esp-modem: guess mode data:", reply, reply_pos, ESP_LOG_DEBUG);
// Check whether the response resembles the "golden" reply (for these 3 protocols)
if (reply_pos >= sizeof(probe::ppp::lcp_echo_reply_head)) {
// check for initial 2 bytes
auto *ptr = static_cast<uint8_t *>(memmem(reply, reply_pos, probe::ppp::lcp_echo_reply_head.data(), 2));
// and check the other two bytes for protocol ID:
// * either LCP reply
if (ptr && ptr[3] == probe::ppp::lcp_echo_reply_head[3] && ptr[4] == probe::ppp::lcp_echo_reply_head[4]) {
if (auto signal = weak_signal.lock()) {
signal->set(probe::ppp::mode);
}
}
// * or LCP conf request
if (ptr && ptr[3] == probe::ppp::lcp_echo_request[3] && ptr[4] == probe::ppp::lcp_echo_request[4]) {
if (auto signal = weak_signal.lock()) {
signal->set(probe::ppp::mode);
if (reply_pos >= 3) { // Minimum size needed for basic PPP detection
// Check for PPP detection - look for both traditional format and alternative formats
// Look for PPP frame delimiter (0x7E)
auto *ppp_start = static_cast<uint8_t *>(memchr(reply, probe::ppp::ppp_delimiter, reply_pos));
if (ppp_start) {
size_t remaining = reply_pos - (ppp_start - reply);
// Look for LCP protocol ID anywhere within reasonable distance after delimiter
if (remaining >= 5) { // Reasonable minimum for finding protocol ID
// Check for original expected pattern
if (memmem(ppp_start, remaining, probe::ppp::lcp_echo_reply_head.data(), 2)) {
// Check for protocol ID in original format position
uint8_t *protocol_pos = ppp_start + 3;
if ((protocol_pos + 1) < (reply + reply_pos) &&
(protocol_pos[0] == probe::ppp::lcp_echo_reply_head[3] &&
protocol_pos[1] == probe::ppp::lcp_echo_reply_head[4])) {
if (auto signal = weak_signal.lock()) {
signal->set(probe::ppp::mode);
return command_result::OK;
}
}
}
// Also check for direct LCP protocol ID after delimiter (alternative format)
if (remaining >= 3 && memmem(ppp_start + 1, remaining - 1,
probe::ppp::lcp_protocol_id.data(),
probe::ppp::lcp_protocol_id.size())) {
if (auto signal = weak_signal.lock()) {
signal->set(probe::ppp::mode);
return command_result::OK;
}
}
}
}
}
if (reply_pos >= 4 && memmem(reply, reply_pos, probe::cmd::reply, sizeof(probe::cmd::reply))) {
if (reply[0] != 0xf9) { // double check that the reply is not wrapped in CMUX headers
if (auto signal = weak_signal.lock()) {
signal->set(probe::cmd::mode);
return command_result::OK;
}
}
}
@ -356,6 +381,7 @@ modem_mode DCE_Mode::guess_unsafe(DTE *dte, bool with_cmux)
if (ptr && (ptr[3] >> 2) == 0) {
if (auto signal = weak_signal.lock()) {
signal->set(probe::cmux::mode);
return command_result::OK;
}
}
}

1
components/esp_modem/src/esp_modem_dte.cpp
View File

@ -359,7 +359,6 @@ void DTE::on_read(got_line_cb on_read_cb)
auto res = on_read_cb(data, len);
if (res == command_result::OK || res == command_result::FAIL) {
primary_term->set_read_cb(nullptr);
internal_lock.unlock();
return true;
}
return false;