From faf51fa52a7462e356927ac521ff4e6ee0703d7c Mon Sep 17 00:00:00 2001 From: Sebastian Hahn Date: Mon, 1 Mar 2010 22:26:44 +0100 Subject: [PATCH] Don't cannibalize one-hop circuits In rare cases, we could cannibalize a one-hop circuit, ending up with a two-hop circuit. This circuit would not be actually used, but we should prevent its creation in the first place. Thanks to outofwords and swissknife for helping to analyse this. --- changes/dont_cannibalize_onehop_circuits | 6 ++++++ src/or/circuitlist.c | 7 ++++++- 2 files changed, 12 insertions(+), 1 deletion(-) create mode 100644 changes/dont_cannibalize_onehop_circuits diff --git a/changes/dont_cannibalize_onehop_circuits b/changes/dont_cannibalize_onehop_circuits new file mode 100644 index 0000000000..10e5fe5f38 --- /dev/null +++ b/changes/dont_cannibalize_onehop_circuits @@ -0,0 +1,6 @@ + o Refactorings: + - Make it explicit that we don't cannibalize one-hop circuits. This happens + in the wild, but doesn't turn out to be a problem because we fortunately + don't use those circuits. Many thanks to outofwords for the initial + analysis and to swissknife who confirmed that two-hop circuits are + actually created. diff --git a/src/or/circuitlist.c b/src/or/circuitlist.c index 73e2e06cce..d71d6a21b0 100644 --- a/src/or/circuitlist.c +++ b/src/or/circuitlist.c @@ -905,6 +905,10 @@ circuit_find_to_cannibalize(uint8_t purpose, extend_info_t *info, int need_capacity = (flags & CIRCLAUNCH_NEED_CAPACITY) != 0; int internal = (flags & CIRCLAUNCH_IS_INTERNAL) != 0; + /* Make sure we're not trying to create a onehop circ by + * cannibalization. */ + tor_assert(!(flags & CIRCLAUNCH_ONEHOP_TUNNEL)); + log_debug(LD_CIRC, "Hunting for a circ to cannibalize: purpose %d, uptime %d, " "capacity %d, internal %d", @@ -920,7 +924,8 @@ circuit_find_to_cannibalize(uint8_t purpose, extend_info_t *info, if ((!need_uptime || circ->build_state->need_uptime) && (!need_capacity || circ->build_state->need_capacity) && (internal == circ->build_state->is_internal) && - circ->remaining_relay_early_cells) { + circ->remaining_relay_early_cells && + !circ->build_state->onehop_tunnel) { if (info) { /* need to make sure we don't duplicate hops */ crypt_path_t *hop = circ->cpath;