software/ors-amarisoft: Provide dedicated TAP interface for each Radio Unit

SlapOS provides to each partition dedicated TAP interface, so that an instance
could organize internal networking. In practice this is used by KVM software
release and here in ors-amarisoft, where we feed to eNB such TAP interface for
CPRI-based radio unit so that eNB, in turn, could provide access to CPRI
Control and Management channel via provided TAP.

However there is a problem: SlapOS provides only one TAP interface per
instance, while we need to have one TAP for each Radio Unit.

-> Solve this problem by creating TAP "subinterfaces" per each RU ourselves.

The interfaces we create are full TAP interfaces, just we name them with prefix
based on main interface, and we allocate only part of address space of sole
SlapOS TAP to each subtap. For example if SlapOS provided us slaptap16 with
2401:5180:0:66:a200::/71 IPv6 range and we want to split it for 2 radio units,
we'll be splitting it into 3 regions as follows:

    slaptap16: split 2401:5180:0:66:a200::/71 by 2
    preserve         2401:5180:0:66:a200::/73
    -> slaptap16-1   2401:5180:0:66:a280::/73
    -> slaptap16-2   2401:5180:0:66:a300::/73

Here we preserve 2401:5180:0:66:a200::/73 for usage on original slaptap16, and
we create slaptap16-1 and slaptap16-2 with correspondingly allocated address
range subparts for the RUs.

The splitting is done easily but depends on having networking administration
capability to be able to work. We solve this with employing
/opt/amarisoft/setcap, which we already use for dnsmasq, and with compiled
trampoline program because setcap does not really work directly on scripts.

To avoid hard dependency on having network capability rights, we fallback to
using regular SlapOS slaptap in case there is only one RU.

ru/lopcomm/* and enb.cfg are adapted straightforwardly, but dnsmasq adaptation
is left to a later step not to mix everything into one pile.

NOTE that relying on setcap is not a good in the long term and should be
     reworked once SlapOS is improved to provide ability for instances to
     request several TAP interfaces. Please see discussion at
     nexedi/slapos!1471 (comment 194356)
     for details.

/cc @jhuge, @lu.xu, @xavier_thompson, @Daetalus
/reviewed-on nexedi/slapos!1471

software/ors-amarisoft/buildout.hash.cfg

@@ -16,7 +16,7 @@
 
 [template]
 filename = instance.cfg
-md5sum = 4a38fac68d3a6ca8d9114673cfa42b77
+md5sum = b2f62658035bd70231a57fcd753f0035
 
 [amarisoft-stats.jinja2.py]
 _update_hash_filename_ = amarisoft-stats.jinja2.py
@@ -28,7 +28,7 @@ md5sum = ab666fdfadbfc7d8a16ace38d295c883
 
 [ru_libinstance.jinja2.cfg]
 _update_hash_filename_ = ru/libinstance.jinja2.cfg
-md5sum = 09cc6f04c43ef3a00519f585716343d9
+md5sum = 46f5ba10f37f188806b5c5de104dc185
 
 [ru_sdr_libinstance.jinja2.cfg]
 _update_hash_filename_ = ru/sdr/libinstance.jinja2.cfg
@@ -36,7 +36,7 @@ md5sum = c20b620111a4dc4bc2bcae57c2007cbe
 
 [ru_lopcomm_libinstance.jinja2.cfg]
 _update_hash_filename_ = ru/lopcomm/libinstance.jinja2.cfg
-md5sum = e67ccf369ccd016e38c5be42442edeae
+md5sum = 02a7a12b933544b4287599afed0fc68d
 
 [ru_sunwave_libinstance.jinja2.cfg]
 _update_hash_filename_ = ru/sunwave/libinstance.jinja2.cfg
@@ -48,27 +48,35 @@ md5sum = 6f8d0592cc4b0b695cea5a0c25aafc4e
 
 [ru_lopcomm_stats.jinja2.py]
 _update_hash_filename_ = ru/lopcomm/stats.jinja2.py
-md5sum = b861ef43beba4a0a2904e8c2aee04723
+md5sum = 3a5a3c5588e1698ee81e983bb08e70d7
 
 [ru_lopcomm_config.jinja2.py]
 _update_hash_filename_ = ru/lopcomm/config.jinja2.py
-md5sum = f2f550b68c8ab243ce1a4bb73a9abc1c
+md5sum = 167537a6aa2762355ee703d4c96351ea
 
 [ru_lopcomm_reset-info.jinja2.py]
 _update_hash_filename_ = ru/lopcomm/reset-info.jinja2.py
-md5sum = e03d7fea24566aa8291f0dc4aaf09c67
+md5sum = 3d78df1993211efaabd3dc6f2ec8de30
 
 [ru_lopcomm_reset.jinja2.py]
 _update_hash_filename_ = ru/lopcomm/reset.jinja2.py
-md5sum = 63472d5dc9bd46923d3941b5189e2ccd
+md5sum = 9741fbc99aaf768e9cc3ab48925dfee5
 
 [ru_lopcomm_software.jinja2.py]
 _update_hash_filename_ = ru/lopcomm/software.jinja2.py
-md5sum = f36eef13210ff519f6a6e56f081f397a
+md5sum = 2b08bb666c5f3ab287cdddbfdb4c9249
 
 [ru_lopcomm_supervision.jinja2.py]
 _update_hash_filename_ = ru/lopcomm/supervision.jinja2.py
-md5sum = 11623b42a0b6271ba0abc8b40e7630e5
+md5sum = 437cc45f132d6c74647a716c6a1920e1
+
+[ru_tapsplit]
+_update_hash_filename_ = ru/tapsplit
+md5sum = 2b8b57c5771b2a2203c0e7767e629e55
+
+[ru_capdo.c]
+_update_hash_filename_ = ru/capdo.c
+md5sum = 52da9fe3a569199e35ad89ae1a44c30e
 
 [template-enb]
 _update_hash_filename_ = instance-enb.jinja2.cfg
@@ -100,7 +108,7 @@ md5sum = dcaac06553a3222b14c0013a13f4a149
 
 [enb.jinja2.cfg]
 filename = config/enb.jinja2.cfg
-md5sum = 8bcf0524a89da28a0329ae598165684b
+md5sum = 8e49dfc9318da43bd817b8891cba24b7
 
 [drb_lte.jinja2.cfg]
 filename = config/drb_lte.jinja2.cfg

software/ors-amarisoft/config/enb.jinja2.cfg

@@ -84,18 +84,7 @@
           {{ cell_list[k].get('cpri_tx_dbm', 0) }}
         {%- endfor -%}
         ",
-      ifname: "
-        {%- if cell_count == 1 -%}
-          {{ slap_configuration.get('tap-name', '') }}
-        {%- else -%}
-          {%- for i, k in enumerate(cell_list) %}
-          {%- if i != 0 -%}
-          ,
-          {%- endif -%}
-            {{ slap_configuration.get('tap-name', '') }}-{{ i }}
-          {%- endfor -%}
-        {%- endif -%}
-        ",
+      ifname: "{{ cell_list.values() | map(attribute='_tap') | join(',') }}",
   },
   tx_gain: 0,
   rx_gain: 0,

software/ors-amarisoft/instance.cfg

@@ -29,6 +29,7 @@ context =
     key eggs_directory buildout:eggs-directory
     key develop_eggs_directory buildout:develop-eggs-directory
     raw buildout_directory ${buildout:directory}
+    raw pythonwitheggs ${buildout:bin-directory}/pythonwitheggs
     section slap_connection slap-connection
     key slapparameter_dict slap-configuration:configuration
     key lan_ipv4 lan-ip:ipv4
@@ -268,6 +269,7 @@ extra-context =
     raw monitor_template ${monitor2-template:output}
     section ors_version ors-version
     section ors_id ors-id
+    section slap_configuration slap-configuration
     key lte_version amarisoft:lte-version
     key lte_expiration amarisoft:lte-expiration
     key enb amarisoft:enb
@@ -287,6 +289,8 @@ extra-context =
     raw ru_lopcomm_cu_config_template   ${ru_lopcomm_cu_config.jinja2.xml:target}
     raw ru_lopcomm_firmware_path ${ru_lopcomm_firmware-dl:target}
     raw ru_lopcomm_firmware_filename ${ru_lopcomm_firmware-dl:filename}
+    raw ru_tapsplit ${ru_tapsplit:target}
+    raw netcapdo ${netcapdo:exe}
     raw openssl_location ${openssl:location}
     raw default_lte_bandwidth ${default-params:default-lte-bandwidth}
     raw default_lte_inactivity_timer ${default-params:default-lte-inactivity-timer}

software/ors-amarisoft/ru/buildout.cfg

@@ -6,5 +6,27 @@ extends =
   lopcomm/buildout.cfg
   sunwave/buildout.cfg
 
+parts +=
+  netcapdo
+  setcap-netcapdo
+
+
 [ru_libinstance.jinja2.cfg]
 <= download-base
+
+[ru_tapsplit]
+<= download-base
+
+[ru_capdo.c]
+<= download-base
+
+[netcapdo]
+recipe = plone.recipe.command
+exe = ${buildout:directory}/netcapdo
+command = gcc ${:ccflags} -o ${:exe} ${ru_capdo.c:target} -lcap
+ccflags = -I${libcap:location}/include -L${libcap:location}/lib -Wl,-rpath=${libcap:location}/lib
+stop-on-error = true
+
+[setcap-netcapdo]
+<= setcap
+exe = ${netcapdo:exe}

software/ors-amarisoft/ru/capdo.c

+// Copyright (C) 2023  Nexedi SA and Contributors.
+//
+// This program is free software: you can Use, Study, Modify and Redistribute
+// it under the terms of the GNU General Public License version 3, or (at your
+// option) any later version, as published by the Free Software Foundation.
+//
+// You can also Link and Combine this program with other software covered by
+// the terms of any of the Free Software licenses or any of the Open Source
+// Initiative approved licenses and Convey the resulting work. Corresponding
+// source of such a combination shall include the source code for all other
+// software used.
+//
+// This program is distributed WITHOUT ANY WARRANTY; without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//
+// See COPYING file for full licensing terms.
+// See https://www.nexedi.com/licensing for rationale and options.
+
+// Program `capdo prog ...` executes prog with inherited capabilities.
+// It is used as trampoline to run scripts under setcap environment.
+//
+// TODO Relying on setcap should be removed once SlapOS is improved to provide
+//      several TAP interfaces to instances. See discussion at
+//      https://lab.nexedi.com/nexedi/slapos/merge_requests/1471#note_194356
+//      for details.
+
+#include <errno.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/capability.h>
+#include <sys/prctl.h>
+
+static int die(const char *fmt, ...);
+static int die_err(const char *msg);
+
+int main(int argc, const char *argv[]) {
+    cap_t caps;
+    cap_value_t cap;
+    cap_flag_value_t flag;
+    uint64_t capbits = 0;
+
+    if (argc < 2)
+        die("usage: capdo prog arguments...");
+
+    // permitted -> inheritable  (so that we can raise ambient below)
+    caps = cap_get_proc();
+    if (!caps)
+        die("cap_get_proc failed");
+    for (cap = 0; cap < CAP_LAST_CAP; cap++) {
+        if (cap_get_flag(caps, cap, CAP_PERMITTED, &flag)) {
+            if (errno = EINVAL)
+                continue; // this cap is not supported by running kernel
+            die_err("cap_get_flag");
+        }
+        if (flag) {
+            cap_set_flag(caps, CAP_INHERITABLE, 1, &cap, flag)  && die_err("cap_set_flag");
+            capbits |= (1ULL << cap);
+        }
+    }
+    cap_set_proc(caps) && die_err("cap_set_proc");
+
+    // raise ambient capabilities to what is permitted/inheritable
+    // this way executed program will have the same capabilities that we have
+    for (cap = 0; cap <= CAP_LAST_CAP; cap++) {
+        if (capbits & (1ULL << cap))
+            prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0)  && die_err("prctl ambient raise");
+    }
+
+    // tail to exec target
+    argv++;
+    execv(argv[0], argv);
+
+    // the only chance we are here is due to exec error
+    die_err(argv[0]);
+}
+
+static int die(const char* fmt, ...) {
+    va_list ap;
+
+    fprintf(stderr, "E: capdo: ");
+
+    va_start(ap, fmt);
+    vfprintf(stderr, fmt, ap);
+    va_end(ap);
+
+    fprintf(stderr, "\n");
+    exit(128);
+    return 0;
+}
+
+static int die_err(const char* msg) {
+    return die("%s: %s", msg, strerror(errno));
+}

software/ors-amarisoft/ru/libinstance.jinja2.cfg

@@ -39,6 +39,82 @@ config-stats-period = {{ slapparameter_dict.get("enb_stats_fetch_period", 60) }}
                                  lopcomm=rudrv_lopcomm,
                                  sunwave=rudrv_sunwave) %}
 
+{#-   slaptap indicates tap interface, that slapos told us to use,
+      or 'xxx-notap-xxx' if slapos provided us either nothing or empty string. #}
+{%-   set slaptap = slap_configuration.get('tap-name', '')   %}
+{%-   if slaptap == '' %}
+{%-     set slaptap = 'xxx-notap-xxx'   %}
+{%-   endif %}
+
+{#-   split slapos tap interface for each RU
+      fallback to non-split approach for ntap <= 1 to avoid hard-dependecy on setcap/tapsplit
+
+      TODO Relying on setcap and tapsplit should be removed once SlapOS is improved to
+           provide several TAP interfaces to instances. See discussion at
+           https://lab.nexedi.com/nexedi/slapos/merge_requests/1471#note_194356
+           for details. #}
+{%-   set ntap = len(list(cell_list|dictsort)) %}
+[vtap]
+recipe = plone.recipe.command
+ntap = {{ ntap }}
+command = {{ netcapdo }} {{ pythonwitheggs }} {{ ru_tapsplit }} {{ slaptap }} ${:ntap}
+update-command = ${:command}
+stop-on-error = true
+
+{%-   if ntap <= 1  %}
+[vtap]
+ntap = 0
+stop-on-error = false
+
+{%-     if ntap == 1  %}
+[vtap.{{ slaptap }}]
+network = {{ slap_configuration['tap-ipv6-network'] }}
+gateway = {{ slap_configuration['tap-ipv6-gateway'] }}
+addr    = {{ slap_configuration['tap-ipv6-addr'] }}
+{%-     endif %}
+
+{%-   else  %}
+
+{%-   for i in range(1,1+ntap)  %}
+{%-     set tap = '%s-%d' % (slaptap, i)   %}
+[vtap.{{ tap }}]
+recipe = slapos.recipe.build
+depends = ${vtap:recipe}
+init =
+  import types
+  def readfile(path):
+    with open(path) as f:
+      return f.read()
+
+  # ~ import tapsplit
+  tapsplit = types.ModuleType('tapsplit')
+  exec(readfile('{{ ru_tapsplit }}'), tapsplit.__dict__)
+
+  # simulate what tapsplit would assign to the tap
+  # ( tap subinterface will be created for real later at install time - when it
+  #   is too late to update section options )
+  slapnet = tapsplit.ifnet6('{{ slaptap }}')
+  tapnet  = tapsplit.netsplit(slapnet, {{ 1+ntap }}) [{{ i }}]
+
+  options['network'] = str(tapnet)
+  options['gateway'] = str(tapnet[1])
+  options['addr']    = str(tapnet[-1])
+{%-   endfor  %}
+
+{%-   endif %}
+
+
+{#-   assign TAP interfaces to RUs                              #}
+{%-   for i, (cell_ref, cell) in enumerate(cell_list|dictsort)  %}
+{%-     if len(cell_list) > 1                                   %}
+{%-       set ru_tap = "%s-%d" % (slaptap, i+1)                 %}
+{%-     else                                                    %}
+{%-       set ru_tap = slaptap                                  %}
+{%-     endif                                                   %}
+{%-     do cell.update({'_tap': ru_tap})                        %}
+{%-   endfor                                                    %}
+
+
 {#-   go through all RUs and for each RU invoke
       RU-specific buildout handler #}
 {%-   set ru_type = {'lopcomm': 'lopcomm', 'm2ru': 'sunwave'}.get(ru, 'sdr') %}

software/ors-amarisoft/ru/lopcomm/config.jinja2.py

@@ -8,7 +8,7 @@ if __name__ == '__main__':
   nc = LopcommNetconfClient(log_file="{{ log_file }}")
   while True:
       try:
-          nc.connect("{{ netaddr.IPAddress(slap_configuration.get('tap-ipv6-gateway', '')) }}", 830, "oranuser", "oranpassword")
+          nc.connect("{{ netaddr.IPAddress(vtap.gateway) }}", 830, "oranuser", "oranpassword")
           nc.edit_config(["{{ CreateProcessingEle_template }}", "{{ cu_config_template }}"])
           break
       except Exception as e:

software/ors-amarisoft/ru/lopcomm/libinstance.jinja2.cfg

@@ -6,7 +6,7 @@
 
 {{ promise('%s-netconf-socket' % ru_ref) }}
 promise = check_socket_listening
-config-host = ${slap-configuration:tap-ipv6-gateway}
+config-host = ${vtap.{{cell._tap}}:gateway}
 config-port = 830
 
 
@@ -21,7 +21,7 @@ supervision-reply-json-log-output = ${:_logbase}-reply.json.log
 is_netconf_connected = ${directory:etc}/{{ru_ref}}.is_netconf_connected
 context =
   section directory directory
-  section slap_configuration slap-configuration
+  section vtap vtap.{{ cell._tap }}
   key slapparameter_dict slap-configuration:configuration
   key log_file :log-output
   key supervision_reply_json_log_file :supervision-reply-json-log-output
@@ -59,7 +59,7 @@ remote-file-path = sftp://${user-info:pw-name}@[${slap-configuration:ipv6-random
 is_firmware_updated = ${directory:etc}/{{ru_ref}}.is_firmware_updated
 context =
   section directory directory
-  section slap_configuration slap-configuration
+  section vtap vtap.{{ cell._tap }}
   key slapparameter_dict slap-configuration:configuration
   key log_file :log-output
   key software_reply_json_log_file :software-reply-json-log-output
@@ -104,8 +104,7 @@ extensions = jinja2.ext.do
 log-output = ${directory:var}/log/{{ru_ref}}-config.log
 context =
   section directory directory
-  section slap_configuration slap-configuration
-  key slapparameter_dict slap-configuration:configuration
+  section vtap vtap.{{ cell._tap }}
   key log_file :log-output
   raw testing {{ slapparameter_dict.get("testing", False) }}
   raw python_path {{ buildout_directory}}/bin/pythonwitheggs
@@ -136,7 +135,7 @@ ncsession-json-log-output = ${:_logbase}-ncsession.json.log
 software-json-log-output = ${:_logbase}-software.json.log
 context =
   section directory directory
-  section slap_configuration slap-configuration
+  section vtap vtap.{{ cell._tap }}
   key slapparameter_dict slap-configuration:configuration
   key log_file :log-output
   key json_log_file :json-log-output
@@ -206,7 +205,7 @@ _logbase = ${directory:var}/log/{{ru_ref}}-reset-info
 log-output = ${:_logbase}.log
 json-log-output = ${:_logbase}.json.log
 context =
-  section slap_configuration slap-configuration
+  section vtap vtap.{{ cell._tap }}
   key log_file :log-output
   key json_log_file :json-log-output
   raw stats_period {{ slapparameter_dict.get("enb_stats_fetch_period", 60) }}
@@ -224,7 +223,7 @@ _logbase = ${directory:var}/log/{{ru_ref}}-reset
 log-output = ${:_logbase}.log
 json-log-output = ${:_logbase}.json.log
 context =
-  section slap_configuration slap-configuration
+  section vtap vtap.{{ cell._tap }}
   key log_file :log-output
   raw python_path {{ buildout_directory}}/bin/pythonwitheggs
   raw buildout_directory_path {{ buildout_directory }}

software/ors-amarisoft/ru/lopcomm/reset-info.jinja2.py

@@ -19,7 +19,7 @@ def get_uptime(hostname, username, password):
         client.close()
 
 # Usage
-hostname = "{{ netaddr.IPAddress(slap_configuration.get('tap-ipv6-gateway', '')) }}"
+hostname = "{{ netaddr.IPAddress(vtap.gateway) }}"
 username = "oranuser"
 password = "oranpassword"
 

software/ors-amarisoft/ru/lopcomm/reset.jinja2.py

@@ -7,7 +7,7 @@ from ncclient_common import LopcommNetconfClient
 if __name__ == '__main__':
     nc = LopcommNetconfClient(log_file="{{ log_file }}")
     try:
-        nc.connect("{{ netaddr.IPAddress(slap_configuration.get('tap-ipv6-gateway', '')) }}", 830, "oranuser", "oranpassword")
+        nc.connect("{{ netaddr.IPAddress(vtap.gateway) }}", 830, "oranuser", "oranpassword")
         nc.reset_device()
         nc.logger.info("Device reset successful.")
     except Exception as e:

software/ors-amarisoft/ru/lopcomm/software.jinja2.py

@@ -16,7 +16,7 @@ if __name__ == '__main__':
   while True:
       try:
           firmware_check_file= '{{ is_firmware_updated }}'
-          nc.connect("{{ netaddr.IPAddress(slap_configuration.get('tap-ipv6-gateway', '')) }}", 830, "oranuser", "oranpassword")
+          nc.connect("{{ netaddr.IPAddress(vtap.gateway) }}", 830, "oranuser", "oranpassword")
           # Fetch software inventory
 
           inventory_vars = nc.get_inventory()

software/ors-amarisoft/ru/lopcomm/stats.jinja2.py

@@ -15,7 +15,7 @@ if __name__ == '__main__':
     )
   while True:
     try:
-        nc.connect("{{ netaddr.IPAddress(slap_configuration.get('tap-ipv6-gateway', '')) }}", 830, "oranuser", "oranpassword")
+        nc.connect("{{ netaddr.IPAddress(vtap.gateway) }}", 830, "oranuser", "oranpassword")
         nc.subscribe()
         while True:
           nc.get_notification()

software/ors-amarisoft/ru/lopcomm/supervision.jinja2.py

@@ -15,7 +15,7 @@ if __name__ == '__main__':
     )
     try:
         netconf_check_file = '{{ is_netconf_connected }}'
-        nc.connect("{{ netaddr.IPAddress(slap_configuration.get('tap-ipv6-gateway', '')) }}", 830, "oranuser", "oranpassword")
+        nc.connect("{{ netaddr.IPAddress(vtap.gateway) }}", 830, "oranuser", "oranpassword")
 
         supervision_subscription_rpc_xml = """
             <create-subscription xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">

software/ors-amarisoft/ru/tapsplit

+#!/usr/bin/env python
+# Copyright (C) 2023  Nexedi SA and Contributors.
+#
+# This program is free software: you can Use, Study, Modify and Redistribute
+# it under the terms of the GNU General Public License version 3, or (at your
+# option) any later version, as published by the Free Software Foundation.
+#
+# You can also Link and Combine this program with other software covered by
+# the terms of any of the Free Software licenses or any of the Open Source
+# Initiative approved licenses and Convey the resulting work. Corresponding
+# source of such a combination shall include the source code for all other
+# software used.
+#
+# This program is distributed WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See COPYING file for full licensing terms.
+# See https://www.nexedi.com/licensing for rationale and options.
+"""Program tapsplit brings tap interface into state with several children
+interfaces each covering part of original interface address space.
+
+Usage: tapsplit <interface> <nchildren>
+"""
+
+# TODO Relying on tapsplit should be removed once SlapOS is improved to provide
+#      several TAP interfaces to instances. See discussion at
+#      https://lab.nexedi.com/nexedi/slapos/merge_requests/1471#note_194356
+#      for details.
+
+import netifaces
+import netaddr
+from socket import AF_INET6
+from math import log2, ceil
+
+import sys
+import subprocess
+
+
+def main():
+    tap = sys.argv[1]
+    n   = int(sys.argv[2])
+    assert n >= 0, n
+
+    # determine tap's network address and owner
+    owner = readfile(sysnet(tap) + '/owner') .strip()
+    net   = ifnet6(tap)
+
+    print('%s: split %s by %d' % (tap, net, n))
+
+    # cleanup existing children
+    for ifname in netifaces.interfaces():
+        if ifname.startswith('%s-' % tap):
+            run('ip', 'link', 'del', ifname)
+
+    # do the split
+    # with leaving first range for the original tap
+    for i, subnet in enumerate(netsplit(net, 1+n)):
+        if i == 0:
+            print('preserve         %s' % subnet)
+            continue    # leave this range for original tap
+        subtap = '%s-%d' % (tap, i)
+        print('-> %s   %s' % (subtap, subnet))
+        run('ip', 'tuntap', 'add', 'dev', subtap, 'mode', 'tap', 'user', owner)
+        run('ip', 'link',   'set', subtap, 'up')
+        run('ip', 'addr',   'add', str(subnet), 'dev', subtap, 'noprefixroute')
+        run('ip', 'route',  'add', str(subnet[1]), 'dev', subtap)
+        run('ip', 'route',  'add', str(subnet), 'dev', subtap, 'via', str(subnet[1]))
+
+
+# netsplit splits network into n subnetworks.
+def netsplit(net, n): # -> []subnet
+    # see how much prefix bits we need to take to be able to divide by n
+    ptake = ceil(log2(n))
+    return list( net.subnet(net.prefixlen + ptake) )[:n]
+
+# ifnet6 returns IPv6 network address associated with given interface.
+def ifnet6(ifname):
+    addr  = None
+    net   = None
+    prefixlen = None
+    for iaddr in netifaces.ifaddresses(ifname)[AF_INET6]:
+        a = iaddr['addr']
+        if '%' in a: # link-local
+            a = a.split('%')[0]
+            a = netaddr.IPAddress(a)
+            assert a.is_link_local(), a
+            continue
+
+        if addr is not None:
+            raise RuntimeError('%s: multiple addresses:  %s and %s' % (ifname, addr, a))
+
+        addr = netaddr.IPAddress(a)
+        netmask, plen = iaddr['netmask'].split('/')
+        prefixlen = int(plen)
+        net = netaddr.IPNetwork('%s/%d' % (a, prefixlen))
+
+    if addr is None:
+        raise RuntimeError('%s: no non link-local addresses' % ifname)
+
+    # normalize network
+    # ex 2401:5180:0:66:a7ff:ffff:ffff:ffff/71  ->  2401:5180:0:66:a600::/71
+    net = net.cidr
+    return net
+
+# sysnet returns path on /sys corresponding to given interface.
+def sysnet(ifname):
+    return '/sys/devices/virtual/net/%s' % ifname
+
+def run(*argv):
+    print(' # %s' % ' '.join(argv))
+    subprocess.check_call(argv)
+
+def readfile(path):
+    with open(path) as f:
+        return f.read()
+
+
+if __name__ == '__main__':
+    main()

software/ors-amarisoft/software-base.cfg

@@ -15,6 +15,7 @@ extends =
   ../../component/dnsmasq/buildout.cfg
   ../../component/fluent-bit/buildout.cfg
   ../../component/openssh/buildout.cfg
+  ../../component/libcap/buildout.cfg
   ru/buildout.cfg
 
 parts +=
@@ -43,7 +44,7 @@ parts +=
   dnsmasq
   eggs
   xamari
-  setcap
+  setcap-dnsmasq
 # unimplemented parts - the http monitor and better log handling using logrotate
 #  apache-php
 #  logrotate
@@ -170,6 +171,8 @@ eggs =
   xmltodict
   ncclient
   ${lxml-python:egg}
+  netifaces
+  netaddr
 interpreter = pythonwitheggs
 
 [xlte-repository]
@@ -193,9 +196,13 @@ scripts = xamari
 
 [setcap]
 recipe = plone.recipe.command
-command = sudo -n /opt/amarisoft/setcap ${dnsmasq:location}/sbin/dnsmasq || true
+command = sudo -n /opt/amarisoft/setcap ${:exe} || true
 update-command = ${:command}
 
+[setcap-dnsmasq]
+<= setcap
+exe = ${dnsmasq:location}/sbin/dnsmasq
+
 [versions]
 websocket-client = 1.4.2
 ncclient = 0.6.13