Compilation error on Debian 9

Compiling NRPE from the maintenance branch fails on Debian 9, at least failed for me :) with:

*** Configuration summary for nrpe 3.2.1 2017-09-01 ***:

 General Options:
 -------------------------
 NRPE port:    5666
 NRPE user:    nagios
 NRPE group:   nagios
 Nagios user:  nagios
 Nagios group: nagios

Review the options above for accuracy.  If they look okay,
type 'make all' to compile the NRPE daemon and client
or type 'make' to get a list of make options.

root@debian9x64:/tmp/nrpe-maint#
root@debian9x64:/tmp/nrpe-maint# make all
cd ./src/; make
make[1]: Entering directory '/tmp/nrpe-maint/src'
gcc -g -O2 -I/usr/include/openssl -DHAVE_CONFIG_H -I ../include -I ./../include -o nrpe ./nrpe.c ./utils.c ./acl.c -L/usr/lib/x86_64-linux-gnu  -lssl -lcrypto -lnsl
In file included from ../include/common.h:32:0,
                 from ./nrpe.c:38:
./nrpe.c: In function ‘init_ssl’:
./nrpe.c:357:39: error: ‘TLS1_3_VERSION’ undeclared (first use in this function)
    SSL_CTX_set_max_proto_version(ctx, TLS1_3_VERSION);
                                       ^
/usr/include/openssl/ssl.h:1298:59: note: in definition of macro ‘SSL_CTX_set_max_proto_version’
         SSL_CTX_ctrl(ctx, SSL_CTRL_SET_MAX_PROTO_VERSION, version, NULL)
                                                           ^~~~~~~
./nrpe.c:357:39: note: each undeclared identifier is reported only once for each function it appears in
    SSL_CTX_set_max_proto_version(ctx, TLS1_3_VERSION);
                                       ^
/usr/include/openssl/ssl.h:1298:59: note: in definition of macro ‘SSL_CTX_set_max_proto_version’
         SSL_CTX_ctrl(ctx, SSL_CTRL_SET_MAX_PROTO_VERSION, version, NULL)
                                                           ^~~~~~~
Makefile:48: recipe for target 'nrpe' failed
make[1]: *** [nrpe] Error 1
make[1]: Leaving directory '/tmp/nrpe-maint/src'
Makefile:65: recipe for target 'all' failed
make: *** [all] Error 2

Let me know if you need any additional information. Thanks!

NagiosEnterprises / nrpe

Compilation error on Debian 9 #215