README.solaris

Solaris has a limitation on the number of file descriptors (255)
available in stdio, so that fopen() fails if more than
255 file descriptors (sockets) are open. This prevents mibs from 
being loaded after 250 sockets are open, since parse.c uses stdio.

SEan <burke_sp@pacbell.net> investigated this problem, and had this
report on using the SFIO package to solve this problem.

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The SFIO package ( http://www.research.att.com/sw/tools/sfio/ ) 
is a buffered streams IO package that is much more more sophisticated 
than stdio, but it does support stdio API's for backward compatibility,
and that's the aspect that is important here.

To compile with SFIO, we simply add -I/usr/local/sfio/include to the
$CPPFLAGS before compiling net-snmp. This causes SFIO's stdio.h to
preempt Solaris stdio, mapping calls like fopen() and fprintf() to
the SFIO implementations. This produces a libnetsnmp that does not
have the fopen() limitation. Any application that links to this 
libnetsnmp must also be linked to libsfio. 

Here are the two caveats:

1. libsfio exports the functions 'getc' and 'putc', for reasons that
are not clear. These are the only symbols it exports that conflict
with stdio. While getc and putc are traditionally macros, Solaris
makes them functions in multithreaded code (compiled with -mt,
-pthread, or -D_REENTRANT). If your native stdio code links to the
libsfio versions, a crash will result.

There are two solutions to this problem. You may remove getc and putc 
from libsfio, since SFIO defines getc and putc as macros, by doing:

	ar d libsfio.a getc.o
	ar d libsfio.a putc.o

or link to SFIO's stdio compatibility library, libstdio, ahead of
libsfio. This library wraps all of the native stdio calls with 
versions that are safe for native or sfio streams, in case you
need to share streams between SFIO and native stdio codes.

2. libsfio provides 64-bit offsets in fseek(), ftell(). This is
a good thing, since SFIO is intened to avoid needless limitations,
but it means that SFIO's stdio.h defines off_t to be a 64-bit offset. 
Net-SNMP uses readdir(), which returns a struct dirent containing 
a 32-bit off_t, so the code compiled for SFIO doesn't access 
struct dirent's correctly.

There are two solutions to this problem, as well. The first is to
include <dirent.h> at the start of SFIO's stdio.h. Since SFIO 
defines a macro substitution for off_t, this leaves struct dirent's 
definition unchanged.

An alternative, which I haven't verified, is to define _FILE_OFFSET_BITS
to be 64 when compiling libnetsnmp. According to what I see in Solaris's 
/usr/include/sys/feature_tests.h, you can select a 64-bit off_t at 
compile time with this setting, which should make readdir()'s off_t 
compatible with SFIO's ftell(), fseek().

Finally, thanks to Phong Vo and AT&T Labs for a fast, robust and
portable package that solves this headache very neatly.

-SEan <burke_sp@pacbell.net>