Debian 8 pppd 2.4.6 LCP配置失败求助（Ubuntu 22.0可正常连接）

我使用搭载Wireless Logic SIM卡的Teltonika调制解调器，通过Linux pppd守护进程经串口连接网络。目前遇到问题：无法升级的Debian 8系统（pppd 2.4.6）中无法完成认证，最终卡在‘Discarded non-LCP packet when LCP not open’错误；但在Ubuntu 22.0系统（pppd 2.4.9）中使用相同配置可正常连接。

Chat脚本内容 #

TIMEOUT 60
ECHO ON
ABORT '\nBUSY\r'
ABORT '\nERROR\r'
ABORT '\nNO ANSWER\r'
ABORT '\nNO CARRIER\r'
ABORT '\nNO DIALTONE\r'' ATZ
OK 'AT+CGDCONT=1,"IP","wlapn.com"'
OK ATD*99***1#
CONNECT ''

Peer配置文件内容 #

cp-echo-failure 0
lcp-echo-interval 0
#nodetach
debug
connect "/usr/sbin/chat -v -f /etc/chatscripts/wireless-logic"
/dev/ttyUSB0
115200
crtscts
noipdefault
default-asyncmap
defaultroute
nobsdcomp
noauth
passive
persist
ipcp-accept-local
ipcp-accept-remote
user R2PUKSYS
password R2PUKSYS
usepeerdns
lock
novj
show-password

Debian 8下失败的调试日志 #

ATZ
OK
AT+CGDCONT=1,"IP","wlapn.com"
OK
ATD*99***1#
CONNECT
Script /usr/sbin/chat -v -f /etc/chatscripts/gprs finished (pid 3229), status = 0x0
Serial connection established.
using channel 9
Using interface ppp0
Connect: ppp0 <--> /dev/ttyS2
sent [LCP ConfReq id=0x1 <magic 0x9fec45d1> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x2a <asyncmap 0x0> <auth chap MD5> <magic 0xd13c8cca> <pcomp> <accomp>]
sent [LCP ConfRej id=0x2a <asyncmap 0x0>]
rcvd [LCP ConfReq id=0x2b <auth chap MD5> <magic 0xd13c8cca> <pcomp> <accomp>]
sent [LCP ConfAck id=0x2b <auth chap MD5> <magic 0xd13c8cca> <pcomp> <accomp>]
rcvd [LCP DiscReq id=0x2c magic=0xd13c8cca]
sent [LCP ConfReq id=0x1 <magic 0x9fec45d1> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x2d <asyncmap 0x0> <auth chap MD5> <magic 0xd13c9885> <pcomp> <accomp>]
sent [LCP ConfRej id=0x2d <asyncmap 0x0>]
rcvd [LCP ConfReq id=0x2e <auth chap MD5> <magic 0xd13c9885> <pcomp> <accomp>]
sent [LCP ConfAck id=0x2e <auth chap MD5> <magic 0xd13c9885> <pcomp> <accomp>]
rcvd [LCP DiscReq id=0x2f magic=0xd13c9885]
LCP: timeout sending Config-Requests
rcvd [CHAP Challenge id=0x2 <fa05d11a50d2b1b27348a897aa62ab92>, name = "UMTS_CHAP_SRVR"]
Discarded non-LCP packet when LCP not open
rcvd [CHAP Challenge id=0x3 <0692e9e924970fcd3bc39cf1c0ebdfaf>, name = "UMTS_CHAP_SRVR"]
Discarded non-LCP packet when LCP not open
rcvd [CHAP Challenge id=0x4 <a513a0bbc0a57e3769a6cf74883dc16e>, name = "UMTS_CHAP_SRVR"]
Discarded non-LCP packet when LCP not open
rcvd [CHAP Challenge id=0x5 <62434f6aabb3f3c981c572115fcb298c>, name = "UMTS_CHAP_SRVR"]
Discarded non-LCP packet when LCP not open
rcvd [CHAP Challenge id=0x6 <4e25351af6614f8d2cd4921f49186666>, name = "UMTS_CHAP_SRVR"]
Discarded non-LCP packet when LCP not open

Ubuntu下正常连接的调试日志 #

OK
AT+CGDCONT=1,"IP","wlapn.com"
OK
ATD*99***1#
CONNECT
Script /usr/sbin/chat -v -f /etc/chatscripts/wireless-logic finished (pid 8876), status = 0x0
Serial connection established.
using channel 1
Using interface ppp0
Connect: ppp0 <--> /dev/ttyUSB0
sent [LCP ConfReq id=0x1 <magic 0x77d321f9> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x0 <asyncmap 0x0> <auth chap MD5> <magic 0x2d03c0b> <pcomp> <accomp>]
sent [LCP ConfRej id=0x0 <asyncmap 0x0>]
rcvd [LCP ConfAck id=0x1 <magic 0x77d321f9> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <auth chap MD5> <magic 0x2d03c0b> <pcomp> <accomp>]
sent [LCP ConfAck id=0x1 <auth chap MD5> <magic 0x2d03c0b> <pcomp> <accomp>]
rcvd [LCP DiscReq id=0x2 magic=0x2d03c0b]
rcvd [CHAP Challenge id=0x1 <b85176b8ba400effcb027573e0394a5e>, name = "UMTS_CHAP_SRVR"]
sent [CHAP Response id=0x1 <97247cf226529819c7d9cf5a16345f7c>, name = "********"]
rcvd [CHAP Success id=0x1 ""]
CHAP authentication succeeded
CHAP authentication succeeded
sent [CCP ConfReq id=0x1 <deflate 15> <deflate(old#) 15>]
sent [IPCP ConfReq id=0x1 <addr 0.0.0.0> <ms-dns1 0.0.0.0> <ms-dns2 0.0.0.0>]
sent [IPV6CP ConfReq id=0x1 <addr fe80::2c99:da39:1484:84a0>]
rcvd [LCP ProtRej id=0x3 80 fd 01 01 00 0c 1a 04 78 00 18 04 78 00]
Protocol-Reject for 'Compression Control Protocol' (0x80fd) received
rcvd [IPCP ConfReq id=0x0]
sent [IPCP ConfNak id=0x0 <addr 0.0.0.0>]
rcvd [IPCP ConfNak id=0x1 <addr 10.94.158.0> <ms-dns1 10.4.0.240> <ms-dns2 10.4.0.230>]
sent [IPCP ConfReq id=0x2 <addr 10.94.158.0> <ms-dns1 10.4.0.240> <ms-dns2 10.4.0.230>]
rcvd [IPCP ConfReq id=0x1]
sent [IPCP ConfAck id=0x1]
rcvd [IPCP ConfAck id=0x2 <addr 10.94.158.0> <ms-dns1 10.4.0.240> <ms-dns2 10.4.0.230>]
Could not determine remote IP address: defaulting to 10.64.64.64
Script /etc/ppp/ip-pre-up started (pid 8888)
Script /etc/ppp/ip-pre-up finished (pid 8888), status = 0x0
not replacing default route to wlp59s0 [10.20.31.254]
local  IP address 10.94.158.0
remote IP address 10.64.64.64
primary   DNS address 10.4.0.240
secondary DNS address 10.4.0.230
Script /etc/ppp/ip-up started (pid 8893)
Script /etc/ppp/ip-up finished (pid 8893), status = 0x0

解决思路建议 #

• 调整LCP协商参数：在peer配置中添加lcp-max-configure 10（增加LCP配置请求重试次数）和lcp-configure-timeout 10（延长单次协商超时时间），解决Debian 8下pppd因协商超时导致的LCP断开问题。
• 修改asyncmap配置：移除peer配置中的default-asyncmap，或者主动设置asyncmap 0x0，避免与对端的asyncmap协商冲突，让LCP协商更快完成。
• 强制启用CHAP认证：在peer配置中添加chap参数，明确告知pppd使用CHAP认证，确保LCP协商阶段就做好认证准备，避免后续无法响应CHAP挑战。
• 优化Chat脚本：在Chat脚本的CONNECT ''后添加TIMEOUT 10，确保串口连接建立后给pppd足够的接管时间，避免数据同步问题。
• 尝试替换pppd版本：如果系统允许编译安装软件，可以下载pppd 2.4.9源码在Debian 8上编译安装，直接避开旧版本的协议协商bug。

内容的提问来源于stack exchange，提问作者Peter Deed