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Opened 7 years ago

Last modified 4 years ago

#8372 new defect

MPPE fails quickly on ar71xx with PPTP

Reported by: winders@… Owned by: developers
Priority: normal Milestone: Chaos Calmer 15.05
Component: packages Version: Backfire 10.03.1 RC4
Keywords: mppe pptp Cc:

Description

This problem has been observed on numerous builds 19497, 20728, and the latest 10.03.1-rc4. Observed on a number of ar71xx platforms. Haven't tried non-ar71xx platforms.

Using nomppe in /etc/ppp/options.pptp gives a stable connection, but when MPPE is allowed, a 128-bit MPPE connection is established, and works for perhaps 10 seconds with traffic passing both ways. The log then gives an error "mppe_decompress[0]: FLUSHED bit not set on flag packet!" The connection goes dead. killall -HUP pppd brings it back for another round.

On the server side, have tried various MTU/MRUs, with no change. The same server config (freebsd8+poptop) is working well with many other clients on 128-bit MPPE. (windows,mac,freebsd+pptpclient)

Since it would be expected that this bug would have been discovered a long time ago if it was widespread, I suspect there could be a platform-specific porting issue, or an incompatibility with FreeBSD+poptop.

Most recent test distribution was 10.03.1-rc4:
openwrt-ar71xx-dir-825-b1-squashfs-factory.bin

crda_1.1.0-2_ar71xx.ipk
hostapd_20100705-1_ar71xx.ipk
iw_0.9.21-1_ar71xx.ipk
kmod-ath9k_2.6.32.25+2010-10-19-1_ar71xx.ipk
kmod-ath_2.6.32.25+2010-10-19-1_ar71xx.ipk
kmod-cfg80211_2.6.32.25+2010-10-19-1_ar71xx.ipk
kmod-crypto-aes_2.6.32.25-1_ar71xx.ipk
kmod-crypto-arc4_2.6.32.25-1_ar71xx.ipk
kmod-crypto-core_2.6.32.25-1_ar71xx.ipk
kmod-crypto-sha1_2.6.32.25-1_ar71xx.ipk
kmod-gre_2.6.32.25-1_ar71xx.ipk
kmod-mac80211_2.6.32.25+2010-10-19-1_ar71xx.ipk
kmod-mppe_2.6.32.25-1_ar71xx.ipk
kmod-tun_2.6.32.25-1_ar71xx.ipk
libpcap_1.0.0-2_ar71xx.ipk
luci-app-upnp_0.9+svn6512-1_ar71xx.ipk
miniupnpd_1.4-3_ar71xx.ipk
ntpdate_4.2.6p2-1_ar71xx.ipk
pptp_1.7.1-3_ar71xx.ipk
tcpdump-mini_4.0.0-3_ar71xx.ipk
wireless-tools_29-4_ar71xx.ipk

Attachments (0)

Change History (3)

comment:1 Changed 7 years ago by anonymous

This appears to be a somewhat common problem, across many systems. In the case of this ticket, the problem was a mismatched negotiation; stateless vs. stateful. Forcing both sides to stateless appears to have fixed the problem. The error message and failed link is from a-not-strictly-necessary sanity check that complains about a consequence of the stateless/stateful mismatch.

There might be a negotiation bug here (or in freebsd ppp), but that is beyond me, and probably out of scope for openwrt.

comment:2 Changed 7 years ago by anonymous

Same symtoms with brcm-2.4 (10.03.1-rc4) on Broadcom 5352 (Linksys WRT54GL). Both sides stateless doesn't fix the problem here.

comment:3 Changed 4 years ago by jow

  • Milestone changed from Backfire 10.03.2 to Chaos Calmer (trunk)

Milestone Backfire 10.03.2 deleted

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