nihilist/tor
1
0
Fork 0
mirror of https://gitlab.torproject.org/tpo/core/tor.git synced 2024-11-10 13:13:44 +01:00
Code Issues Packages Projects Releases Wiki Activity

add log convention to hacking file

Browse Source 
this thing needs to get revamped into a 'guide to tor' document


svn:r534
This commit is contained in:
Roger Dingledine 2003-10-03 19:37:38 +00:00
parent 985a3e1492
commit 22526c62a5
1 changed files with 91 additions and 86 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
doc/HACKING
View File

@ -6,31 +6,23 @@ the code, add features, fix bugs, etc.
Read the README file first, so you can get familiar with the basics.
1. The programs.
The pieces.
1.1. "or". This is the main program here. It functions as either a server
or a client, depending on which config file you give it.
1.2. "orkeygen". Use "orkeygen file-for-privkey file-for-pubkey" to
generate key files for an onion router.
2. The pieces.
2.1. Routers. Onion routers, as far as the 'or' program is concerned,
Routers. Onion routers, as far as the 'tor' program is concerned,
are a bunch of data items that are loaded into the router_array when
the program starts. Periodically it downloads a new set of routers
from a directory server, and updates the router_array. When a new OR
connection is started (see below), the relevant information is copied
from the router struct to the connection struct.
2.2. Connections. A connection is a long-standing tcp socket between
Connections. A connection is a long-standing tcp socket between
nodes. A connection is named based on what it's connected to -- an "OR
connection" has an onion router on the other end, an "OP connection" has
an onion proxy on the other end, an "exit connection" has a website or
other server on the other end, and an "AP connection" has an application
proxy (and thus a user) on the other end.
2.3. Circuits. A circuit is a path over the onion routing
Circuits. A circuit is a path over the onion routing
network. Applications can connect to one end of the circuit, and can
create exit connections at the other end of the circuit. AP and exit
connections have only one circuit associated with them (and thus these
@ -38,22 +30,18 @@ connection types are closed when the circuit is closed), whereas OP and
OR connections multiplex many circuits at once, and stay standing even
when there are no circuits running over them.
2.4. Topics. Topics are specific conversations between an AP and an exit.
Topics are multiplexed over circuits.
Streams. Streams are specific conversations between an AP and an exit.
Streams are multiplexed over circuits.
2.4. Cells. Some connections, specifically OR and OP connections, speak
Cells. Some connections, specifically OR and OP connections, speak
"cells". This means that data over that connection is bundled into 256
byte packets (8 bytes of header and 248 bytes of payload). Each cell has
a type, or "command", which indicates what it's for.
Robustness features.
3. Important parameters in the code.
4. Robustness features.
4.1. Bandwidth throttling. Each cell-speaking connection has a maximum
[XXX no longer up to date]
Bandwidth throttling. Each cell-speaking connection has a maximum
bandwidth it can use, as specified in the routers.or file. Bandwidth
throttling can occur on both the sender side and the receiving side. If
the LinkPadding option is on, the sending side sends cells at regularly
@ -75,7 +63,7 @@ The bandwidth throttling uses TCP to push back when we stop reading.
We extend it with token buckets to allow more flexibility for traffic
bursts.
4.2. Data congestion control. Even with the above bandwidth throttling,
Data congestion control. Even with the above bandwidth throttling,
we still need to worry about congestion, either accidental or intentional.
If a lot of people make circuits into same node, and they all come out
through the same connection, then that connection may become saturated
@ -102,7 +90,7 @@ already guarantee in-order delivery of each cell. Rather than trying
to build some sort of tcp-on-tcp scheme, we implement this minimal data
congestion control; so far it's enough.
4.3. Router twins. In many cases when we ask for a router with a given
Router twins. In many cases when we ask for a router with a given
address and port, we really mean a router who knows a given key. Router
twins are two or more routers that share the same private key. We thus
give routers extra flexibility in choosing the next hop in the circuit: if
@ -111,3 +99,20 @@ some of the twins are down or slow, it can choose the more available ones.
Currently the code tries for the primary router first, and if it's down,
chooses the first available twin.
Coding conventions:
Log convention: use only these four log severities.
ERR is if something fatal just happened.
WARNING is something bad happened, but we're still running. The
bad thing is either a bug in the code, an attack or buggy
protocol/implementation of the remote peer, etc. The operator should
examine the bad thing and try to correct it.
(No error or warning messages should be expected. I expect most people
to run on -l warning eventually. If a library function is currently
called such that failure always means ERR, then the library function
should log WARNING and let the caller log ERR.)
INFO means something happened (maybe bad, maybe ok), but there's nothing
you need to (or can) do about it.
DEBUG is for everything louder than INFO.