net-snmp-5.8 build error: ./.libs/libnetsnmpagent.so: undefined reference to `getdtablesize'

[rybasd]

Trying to build net-snmp-5.8 in termux enviroment on android 10
Differences of termux envinronment from typical Linux: https://wiki.termux.com/wiki/Differences_from_Linux

I invoke configure with
./configure --prefix=@PREFIX

First, config.guess did not proceed

UNAME_MACHINE = aarch64
UNAME_RELEASE = 4.14.117-18571899
UNAME_SYSTEM  = Linux
UNAME_VERSION = #2 SMP PREEMPT Thu Jun 4 16:59:11 KST 2020
configure: error: cannot guess build type; you must specify one

I have replaced config.guess and config.sub with what was in my system in /data/data/com.termux/files/usr/share/automake-1.16 and that fixed the issue.

Second, make all throwed errors on undeclared identifier ushort and undeclared type ulong, so I replaced with unsigned short and unsigned long (for details see #154 ) and that fixed the issue

And now, the problem is that make all throws an error: error: ./.libs/libnetsnmpagent.so: undefined reference to getdtablesize'`

The error chunk of output:

libtool: link: gcc -g -O2 -DNETSNMP_ENABLE_IPV6 -fno-strict-aliasing -DNETSNMP_REMOVE_U64 -g -O2 -Ulinux -Dlinux=linux -o .libs/snmpd .libs/snmpd.o ./.libs/libnetsnmpagent.so ./.libs/libnetsnmpmibs.so /data/data/com.termux/files/home/snmp/net-snmp-5.8/agent/.libs/libnetsnmpagent.so /data/data/com.termux/files/home/snmp/net-snmp-5.8/snmplib/.libs/libnetsnmp.so -lnl -lpcre ../snmplib/.libs/libnetsnmp.so -lcrypto -lm -Wl,-rpath -Wl,/data/data/com.termux/files/usr/lib 
/data/data/com.termux/files/usr/bin/aarch64-linux-android-ld: ./.libs/libnetsnmpagent.so: undefined reference to `getdtablesize' 
clang-10: error: linker command failed with exit code 1 (use -v to see invocation) 
make[1]: *** [Makefile:1002: snmpd] Error 1 
make[1]: Leaving directory '/data/data/com.termux/files/home/snmp/net-snmp-5.8/agent' 
make: *** [Makefile:663: subdirs] Error 1
$

Please help to fix.

[csmall]

gdtablesize is checked in the configure step and HAVE_GETSTABLESIZE is defined (or not, as the case may be).
However, agent/netsnmp_close_fds.c doesn't check for this.

If your library has it, then you could use sysconf(_SC_OPEN_MAX) and in fact, the getdtablesize man page suggest this for portable applications. As a last resort, just wrapping the relevant line with #ifdef HAVE_GETDTABLESIZE/#ENDIF will do the job, but other file descriptors won't get closed.

If your version of Linux has /proc/self/fd/ (I'm not sure of how good termux's procfs is) then it will use this value anyway.

[rybasd]

Yes, after googling I have put into include/net-snmp/net-snmp-config.h a line with
#define getdtablesize() sysconf(_SC_OPEN_MAX)
And it worked

[rybasd]

I have put into include/net-snmp/net-snmp-config.h a line with
#define getdtablesize() sysconf(_SC_OPEN_MAX)
And it worked

[rybasd]

I'm not sure if I should close this as I'm novice. I've got a workaround, so that's not an issue for me anymore. Please advise.

[bvanassche]

Please revert the net-snmp-config.h changes and try the following patch instead:

Subject: [PATCH] snmpd, snmptrapd: Let configure check whether getdtablesize()
 is available

This patch fixes the Net-SNMP build for termux.

See also https://github.com/net-snmp/net-snmp/issues/155.
---
 agent/netsnmp_close_fds.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/agent/netsnmp_close_fds.c b/agent/netsnmp_close_fds.c
index 556c3dcfba89..8b75e97cd14d 100644
--- a/agent/netsnmp_close_fds.c
+++ b/agent/netsnmp_close_fds.c
@@ -44,8 +44,13 @@ void netsnmp_close_fds(int fd)
         closedir(dir);
     }
 #endif
-    if (largest_fd < 0)
+    if (largest_fd < 0) {
+#ifdef HAVE_GETDTABLESIZE
         largest_fd = getdtablesize() - 1;
+#else
+        largest_fd = sysconf(_SC_OPEN_MAX);
+#endif
+    }
 
     for (i = largest_fd; i > fd && i >= 0; i--)
         close(i);

[rybasd]

@bvanassche I'm sorry but that says nothing to me. If you give step by step instructions, I would try.

[bvanassche]

The fix has been applied on the V5-9-patches branch and also on the master branch. Please download the latest version of the Net-SNMP source code from either branch and retest.