November 2017 - tor-commits - lists.torproject.org

[tor/maint-0.3.1] Merge branch 'bug21394_029' into maint-0.2.9
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit 072e194a15e9aa0e75c6723763a69476f4f31b93 Merge: 30b322925 982757430 Author: Nick Mathewson <nickm(a)torproject.org> Date: Thu Nov 30 11:48:06 2017 -0500 Merge branch 'bug21394_029' into maint-0.2.9 changes/bug21394 | 9 +++++++++ src/or/dns.c | 23 ++++++++++++++++++++--- 2 files changed, 29 insertions(+), 3 deletions(-)

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[tor/maint-0.3.0] Merge branch 'bug21394_029' into maint-0.2.9
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit 072e194a15e9aa0e75c6723763a69476f4f31b93 Merge: 30b322925 982757430 Author: Nick Mathewson <nickm(a)torproject.org> Date: Thu Nov 30 11:48:06 2017 -0500 Merge branch 'bug21394_029' into maint-0.2.9 changes/bug21394 | 9 +++++++++ src/or/dns.c | 23 ++++++++++++++++++++--- 2 files changed, 29 insertions(+), 3 deletions(-)

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[tor/master] Merge branch 'maint-0.3.1' into maint-0.3.2
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit 25d50decb275854c312c8ee4ce5fd7e3f2945e5c Merge: f0007f2b8 500f04a74 Author: Nick Mathewson <nickm(a)torproject.org> Date: Thu Nov 30 11:48:12 2017 -0500 Merge branch 'maint-0.3.1' into maint-0.3.2

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[tor/master] Merge branch 'maint-0.3.0' into maint-0.3.1
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit 500f04a74e22686f7659adecea02569b3459c71b Merge: 703ab95e9 766d0a2d9 Author: Nick Mathewson <nickm(a)torproject.org> Date: Thu Nov 30 11:48:12 2017 -0500 Merge branch 'maint-0.3.0' into maint-0.3.1 changes/bug21394 | 9 +++++++++ src/or/dns.c | 23 ++++++++++++++++++++--- 2 files changed, 29 insertions(+), 3 deletions(-)

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[tor/release-0.2.9] Merge branch 'bug21394_029' into maint-0.2.9
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit 072e194a15e9aa0e75c6723763a69476f4f31b93 Merge: 30b322925 982757430 Author: Nick Mathewson <nickm(a)torproject.org> Date: Thu Nov 30 11:48:06 2017 -0500 Merge branch 'bug21394_029' into maint-0.2.9 changes/bug21394 | 9 +++++++++ src/or/dns.c | 23 ++++++++++++++++++++--- 2 files changed, 29 insertions(+), 3 deletions(-)

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[tor/release-0.2.9] Fix DNS resolution on busy exit relays
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit 98275743081728b1538f70111c891ea573127e85 Author: Sebastian Hahn <sebastian(a)torproject.org> Date: Fri Nov 3 03:06:12 2017 +0100 Fix DNS resolution on busy exit relays Thanks to Dhalgren who analyzed this issue two years ago and found a solution! --- changes/bug21394 | 9 +++++++++ src/or/dns.c | 23 ++++++++++++++++++++--- 2 files changed, 29 insertions(+), 3 deletions(-) diff --git a/changes/bug21394 b/changes/bug21394 new file mode 100644 index 000000000..e5452e20b --- /dev/null +++ b/changes/bug21394 @@ -0,0 +1,9 @@ + o Major bugfixes (Exit nodes): + - Fix an issue causing high-bandwidth exit nodes to fail a majority + or all of their DNS requests, making them basically unsuitable for + regular usage in Tor circuits. The problem is related to + libevent's DNS handling, but we can work around it in Tor. Fixes + bugs 21394 and 18580; bugfix on 0.1.2.2-alpha which introduced + eventdns. Credit goes to Dhalgren for identifying and finding a + workaround to this bug and to gamambel, arthuredelstein and + arma in helping to track it down and analyze it. diff --git a/src/or/dns.c b/src/or/dns.c index 0ad4c0f50..c1e3c3256 100644 --- a/src/or/dns.c +++ b/src/or/dns.c @@ -1425,14 +1425,31 @@ configure_nameservers(int force) #define SET(k,v) evdns_base_set_option(the_evdns_base, (k), (v)) + // If we only have one nameserver, it does not make sense to back off + // from it for a timeout. Unfortunately, the value for max-timeouts is + // currently clamped by libevent to 255, but it does not hurt to set + // it higher in case libevent gets a patch for this. + // Reducing attempts in the case of just one name server too, because + // it is very likely to be a local one where a network connectivity + // issue should not cause an attempt to fail. if (evdns_base_count_nameservers(the_evdns_base) == 1) { - SET("max-timeouts:", "16"); - SET("timeout:", "10"); + SET("max-timeouts:", "1000000"); + SET("attempts:", "1"); } else { SET("max-timeouts:", "3"); - SET("timeout:", "5"); } + // Elongate the queue of maximum inflight dns requests, so if a bunch + // time out at the resolver (happens commonly with unbound) we won't + // stall every other DNS request. This potentially means some wasted + // CPU as there's a walk over a linear queue involved, but this is a + // much better tradeoff compared to just failing DNS requests because + // of a full queue. + SET("max-inflight:", "8192"); + + // Time out after 5 seconds if no reply. + SET("timeout:", "5"); + if (options->ServerDNSRandomizeCase) SET("randomize-case:", "1"); else

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[tor/release-0.2.9] Merge branch 'maint-0.2.9' into release-0.2.9
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit c8f3af4cecaf4884a8c0b77374f0c19998ec9f2b Merge: c9a3525c7 072e194a1 Author: Nick Mathewson <nickm(a)torproject.org> Date: Thu Nov 30 11:48:12 2017 -0500 Merge branch 'maint-0.2.9' into release-0.2.9 changes/bug21394 | 9 +++++++++ src/or/dns.c | 23 ++++++++++++++++++++--- 2 files changed, 29 insertions(+), 3 deletions(-)

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[tor/master] Merge branch 'maint-0.3.2'
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit 6c355d576354a252c642ff6f3e7781580c007c48 Merge: a1b0a0b9c 25d50decb Author: Nick Mathewson <nickm(a)torproject.org> Date: Thu Nov 30 11:48:12 2017 -0500 Merge branch 'maint-0.3.2'

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[tor/release-0.3.1] Fix DNS resolution on busy exit relays
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit 98275743081728b1538f70111c891ea573127e85 Author: Sebastian Hahn <sebastian(a)torproject.org> Date: Fri Nov 3 03:06:12 2017 +0100 Fix DNS resolution on busy exit relays Thanks to Dhalgren who analyzed this issue two years ago and found a solution! --- changes/bug21394 | 9 +++++++++ src/or/dns.c | 23 ++++++++++++++++++++--- 2 files changed, 29 insertions(+), 3 deletions(-) diff --git a/changes/bug21394 b/changes/bug21394 new file mode 100644 index 000000000..e5452e20b --- /dev/null +++ b/changes/bug21394 @@ -0,0 +1,9 @@ + o Major bugfixes (Exit nodes): + - Fix an issue causing high-bandwidth exit nodes to fail a majority + or all of their DNS requests, making them basically unsuitable for + regular usage in Tor circuits. The problem is related to + libevent's DNS handling, but we can work around it in Tor. Fixes + bugs 21394 and 18580; bugfix on 0.1.2.2-alpha which introduced + eventdns. Credit goes to Dhalgren for identifying and finding a + workaround to this bug and to gamambel, arthuredelstein and + arma in helping to track it down and analyze it. diff --git a/src/or/dns.c b/src/or/dns.c index 0ad4c0f50..c1e3c3256 100644 --- a/src/or/dns.c +++ b/src/or/dns.c @@ -1425,14 +1425,31 @@ configure_nameservers(int force) #define SET(k,v) evdns_base_set_option(the_evdns_base, (k), (v)) + // If we only have one nameserver, it does not make sense to back off + // from it for a timeout. Unfortunately, the value for max-timeouts is + // currently clamped by libevent to 255, but it does not hurt to set + // it higher in case libevent gets a patch for this. + // Reducing attempts in the case of just one name server too, because + // it is very likely to be a local one where a network connectivity + // issue should not cause an attempt to fail. if (evdns_base_count_nameservers(the_evdns_base) == 1) { - SET("max-timeouts:", "16"); - SET("timeout:", "10"); + SET("max-timeouts:", "1000000"); + SET("attempts:", "1"); } else { SET("max-timeouts:", "3"); - SET("timeout:", "5"); } + // Elongate the queue of maximum inflight dns requests, so if a bunch + // time out at the resolver (happens commonly with unbound) we won't + // stall every other DNS request. This potentially means some wasted + // CPU as there's a walk over a linear queue involved, but this is a + // much better tradeoff compared to just failing DNS requests because + // of a full queue. + SET("max-inflight:", "8192"); + + // Time out after 5 seconds if no reply. + SET("timeout:", "5"); + if (options->ServerDNSRandomizeCase) SET("randomize-case:", "1"); else

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[tor/release-0.3.0] Merge branch 'bug21394_029' into maint-0.2.9
by nickm＠torproject.org 30 Nov '17

30 Nov '17

commit 072e194a15e9aa0e75c6723763a69476f4f31b93 Merge: 30b322925 982757430 Author: Nick Mathewson <nickm(a)torproject.org> Date: Thu Nov 30 11:48:06 2017 -0500 Merge branch 'bug21394_029' into maint-0.2.9 changes/bug21394 | 9 +++++++++ src/or/dns.c | 23 ++++++++++++++++++++--- 2 files changed, 29 insertions(+), 3 deletions(-)

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