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! 15: <H2><A NAME="s6">6.</A> <A HREF="prog.html#toc6">System dependent parts</A></H2>
! 16:
! 17: <H2><A NAME="ss6.1">6.1</A> <A HREF="prog.html#toc6.1">Introduction</A>
! 18: </H2>
! 19:
! 20: <P>We've tried to make BIRD as portable as possible, but unfortunately
! 21: communication with the network stack differs from one OS to another,
! 22: so we need at least some OS specific code. The good news is that this
! 23: code is isolated in a small set of modules:
! 24: <P>
! 25: <DL>
! 26: <DT><CODE>config.h</CODE><DD><P>is a header file with configuration information,
! 27: definition of the standard set of types and so on.
! 28: <DT>Startup module<DD><P>controls BIRD startup. Common for a family of OS's (e.g.,
! 29: for all Unices).
! 30: <DT>Logging module<DD><P>manages the system logs. [per OS family]
! 31: <DT>IO module<DD><P>gives an implementation of sockets, timers and the
! 32: global event queue. [per OS family]
! 33: <DT>KRT module<DD><P>implements the Kernel and Device protocols. This
! 34: is the most arcane part of the system dependent stuff and some
! 35: functions differ even between various releases of a single OS.
! 36: </DL>
! 37: <H2><A NAME="ss6.2">6.2</A> <A HREF="prog.html#toc6.2">Logging</A>
! 38: </H2>
! 39:
! 40: <P>
! 41: <P>The Logging module offers a simple set of functions for writing
! 42: messages to system logs and to the debug output. Message classes
! 43: used by this module are described in <CODE>birdlib.h</CODE> and also in the
! 44: user's manual.
! 45: <P>
! 46: <P><HR><H3>Function</H3>
! 47: <P><I>void</I>
! 48: <B>log_commit</B>
! 49: (<I>int</I> <B>class</B>, <I>buffer *</I> <B>buf</B>) -- commit a log message
! 50: <P>
! 51: <H3>Arguments</H3>
! 52: <P>
! 53: <DL>
! 54: <DT><I>int</I> <B>class</B><DD><P>message class information (<I>L_DEBUG</I> to <I>L_BUG</I>, see <CODE>lib/birdlib.h</CODE>)
! 55: <DT><I>buffer *</I> <B>buf</B><DD><P>message to write
! 56: </DL>
! 57: <H3>Description</H3>
! 58: <P>This function writes a message prepared in the log buffer to the
! 59: log file (as specified in the configuration). The log buffer is
! 60: reset after that. The log message is a full line, <B>log_commit()</B>
! 61: terminates it.
! 62: <P>The message class is an integer, not a first char of a string like
! 63: in <B>log()</B>, so it should be written like *L_INFO.
! 64:
! 65:
! 66: <HR><H3>Function</H3>
! 67: <P><I>void</I>
! 68: <B>log_msg</B>
! 69: (<I>const char *</I> <B>msg</B>, <I>...</I> <B>...</B>) -- log a message
! 70: <P>
! 71: <H3>Arguments</H3>
! 72: <P>
! 73: <DL>
! 74: <DT><I>const char *</I> <B>msg</B><DD><P>printf-like formatting string with message class information
! 75: prepended (<I>L_DEBUG</I> to <I>L_BUG</I>, see <CODE>lib/birdlib.h</CODE>)
! 76: <DT><I>...</I> <B>...</B><DD><P>variable arguments
! 77: </DL>
! 78: <H3>Description</H3>
! 79: <P>This function formats a message according to the format string <B>msg</B>
! 80: and writes it to the corresponding log file (as specified in the
! 81: configuration). Please note that the message is automatically
! 82: formatted as a full line, no need to include <CODE>\n</CODE> inside.
! 83: It is essentially a sequence of <B>log_reset()</B>, <B>logn()</B> and <B>log_commit()</B>.
! 84:
! 85:
! 86: <HR><H3>Function</H3>
! 87: <P><I>void</I>
! 88: <B>bug</B>
! 89: (<I>const char *</I> <B>msg</B>, <I>...</I> <B>...</B>) -- report an internal error
! 90: <P>
! 91: <H3>Arguments</H3>
! 92: <P>
! 93: <DL>
! 94: <DT><I>const char *</I> <B>msg</B><DD><P>a printf-like error message
! 95: <DT><I>...</I> <B>...</B><DD><P>variable arguments
! 96: </DL>
! 97: <H3>Description</H3>
! 98: <P>This function logs an internal error and aborts execution
! 99: of the program.
! 100:
! 101:
! 102: <HR><H3>Function</H3>
! 103: <P><I>void</I>
! 104: <B>die</B>
! 105: (<I>const char *</I> <B>msg</B>, <I>...</I> <B>...</B>) -- report a fatal error
! 106: <P>
! 107: <H3>Arguments</H3>
! 108: <P>
! 109: <DL>
! 110: <DT><I>const char *</I> <B>msg</B><DD><P>a printf-like error message
! 111: <DT><I>...</I> <B>...</B><DD><P>variable arguments
! 112: </DL>
! 113: <H3>Description</H3>
! 114: <P>This function logs a fatal error and aborts execution
! 115: of the program.
! 116:
! 117:
! 118: <HR><H3>Function</H3>
! 119: <P><I>void</I>
! 120: <B>debug</B>
! 121: (<I>const char *</I> <B>msg</B>, <I>...</I> <B>...</B>) -- write to debug output
! 122: <P>
! 123: <H3>Arguments</H3>
! 124: <P>
! 125: <DL>
! 126: <DT><I>const char *</I> <B>msg</B><DD><P>a printf-like message
! 127: <DT><I>...</I> <B>...</B><DD><P>variable arguments
! 128: </DL>
! 129: <H3>Description</H3>
! 130: <P>This function formats the message <B>msg</B> and prints it out
! 131: to the debugging output. No newline character is appended.
! 132:
! 133: <H2><A NAME="ss6.3">6.3</A> <A HREF="prog.html#toc6.3">Kernel synchronization</A>
! 134: </H2>
! 135:
! 136: <P>
! 137: <P>This system dependent module implements the Kernel and Device protocol,
! 138: that is synchronization of interface lists and routing tables with the
! 139: OS kernel.
! 140: <P>The whole kernel synchronization is a bit messy and touches some internals
! 141: of the routing table engine, because routing table maintenance is a typical
! 142: example of the proverbial compatibility between different Unices and we want
! 143: to keep the overhead of our KRT business as low as possible and avoid maintaining
! 144: a local routing table copy.
! 145: <P>The kernel syncer can work in three different modes (according to system config header):
! 146: Either with a single routing table and single KRT protocol [traditional UNIX]
! 147: or with many routing tables and separate KRT protocols for all of them
! 148: or with many routing tables, but every scan including all tables, so we start
! 149: separate KRT protocols which cooperate with each other [Linux].
! 150: In this case, we keep only a single scan timer.
! 151: <P>We use FIB node flags in the routing table to keep track of route
! 152: synchronization status. We also attach temporary <I>rte</I>'s to the routing table,
! 153: but it cannot do any harm to the rest of BIRD since table synchronization is
! 154: an atomic process.
! 155: <P>When starting up, we cheat by looking if there is another
! 156: KRT instance to be initialized later and performing table scan
! 157: only once for all the instances.
! 158: <P>The code uses OS-dependent parts for kernel updates and scans. These parts are
! 159: in more specific sysdep directories (e.g. sysdep/linux) in functions krt_sys_*
! 160: and kif_sys_* (and some others like <B>krt_replace_rte()</B>) and krt-sys.h header file.
! 161: This is also used for platform specific protocol options and route attributes.
! 162: <P>There was also an old code that used traditional UNIX ioctls for these tasks.
! 163: It was unmaintained and later removed. For reference, see sysdep/krt-* files
! 164: in commit 396dfa9042305f62da1f56589c4b98fac57fc2f6
! 165: <P>
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