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Implement script null_route_helper (sonic-net#1737)
Signed-off-by: bingwang <bingwang@microsoft.com>
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| #!/usr/bin/env python3 | ||
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| """ | ||
| Utility for blocking and unblocking traffic from given source ip address on ACL tables. | ||
| The block operation will insert a DENY rule at the top of the table. The unblock operation | ||
| will remove an existing DENY rule that has been created by the block operation (i.e. it does | ||
| NOT insert an ALLOW rule, only removes DENY rules). | ||
| Since SONiC supports multi ACL rules share the same priority, all ACL rules created by null_route_helper will | ||
| use the highest priority(9999). | ||
| Example: | ||
| Block traffic from 10.2.3.4: | ||
| ./null_route_helper block acl_table_name 10.2.3.4 | ||
| Unblock all traffic from 10.2.3.4: | ||
| ./null_route_helper unblock acl_table_name 10.2.3.4 | ||
| List all acl rules added by this script | ||
| ./null_route_helper list acl_table_name | ||
| """ | ||
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| from __future__ import print_function | ||
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| import syslog | ||
| import sys | ||
| import click | ||
| import ipaddress | ||
| import tabulate | ||
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| from swsscommon.swsscommon import ConfigDBConnector | ||
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| CONFIG_DB_ACL_TABLE_TABLE = "ACL_TABLE" | ||
| CONFIG_DB_ACL_RULE_TABLE = "ACL_RULE" | ||
| CONFIG_DB_VLAN_TABLE = "VLAN" | ||
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| ACTION_ALLOW = "FORWARD" | ||
| ACTION_DENY = "DROP" | ||
| ACTION_LIST = "LIST" | ||
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| # Since SONiC supports multi ACL rules share the same priority, we use 9999 (the highest) for all rules | ||
| ACL_RULE_PRIORITY = 9999 | ||
| # The key of rule will be overridden with BLOCK_RULE_ + ip | ||
| ACL_RULE_PREFIX = 'BLOCK_RULE_' | ||
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| # Internet Protocol version 4 EtherType | ||
| ETHER_TYPE_IPV4 = 0x0800 | ||
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| def notice(msg): | ||
| """ | ||
| Log a NOTICE message to the console and syslog | ||
| """ | ||
| syslog.syslog(syslog.LOG_NOTICE, msg) | ||
| print(msg) | ||
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| def error(msg): | ||
| """ | ||
| Log an ERR message to the console and syslog, and exit the program with an error code | ||
| """ | ||
| syslog.syslog(syslog.LOG_ERR, msg) | ||
| print(msg, file=sys.stderr) | ||
| sys.exit(1) | ||
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| def ip_ver(ip_prefix): | ||
| return ipaddress.ip_network(ip_prefix, False).version | ||
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| def confirm_required_table_existence(configdb, sub_table_name): | ||
| """ | ||
| Check the existence of required ACL table, and exit if absent | ||
| """ | ||
| target_table = configdb.get_entry(CONFIG_DB_ACL_TABLE_TABLE, sub_table_name) | ||
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| if not target_table: | ||
| error("Table {} not found, exiting...".format(sub_table_name)) | ||
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| return True | ||
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| def get_acl_rule_key(ip_prefix): | ||
| """ | ||
| Get the key that will be used to refer to the ACL rule used to block traffic from a source ip. | ||
| Since the rules are all given the same priority in SONiC, we can't identify a rule based on the priority. | ||
| So, we use the destination IP being blocked to give each rule a unique name in the system. | ||
| """ | ||
| return ACL_RULE_PREFIX + str(ip_prefix) | ||
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| def get_all_acl_rules(configdb, table_name): | ||
| """ | ||
| Return a dict of existed acl rules | ||
| {(u'NULL_ROUTE_TABLE', u'BLOCK_RULE_1.1.1.1/32'): {'PRIORITY': '9999', 'PACKET_ACTION': 'FORWARD', 'SRC_IP': '1.1.1.1/32'},...} | ||
| """ | ||
| key = CONFIG_DB_ACL_RULE_TABLE + '|' + table_name | ||
| all_rules = configdb.get_table(key) | ||
| block_rules = {} | ||
| for k, v in all_rules.items(): | ||
| if k[1].startswith(ACL_RULE_PREFIX): | ||
| block_rules[k] = v | ||
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| return block_rules | ||
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| def validate_input(ip_address): | ||
| """ | ||
| Validate the format of input | ||
| """ | ||
| try: | ||
| ip_n = ipaddress.ip_network(ip_address, False) | ||
| ver = ip_n.version | ||
| prefix_len = ip_n.prefixlen | ||
| # Prefix len must be 32 for IPV4 and 128 for IPV6 | ||
| if ver == 4 and prefix_len == 32 or ver == 6 and prefix_len == 128: | ||
| return ip_n.with_prefixlen | ||
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| error("Prefix length must be 32 (IPv4) or 128 (IPv6)") | ||
| except ValueError as e: | ||
| error("Could not parse {} as a valid IP address; exception={}".format(ip_address, e)) | ||
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| def build_acl_rule(priority, src_ip): | ||
| """ | ||
| Bild DROP rule for given src_ip and priority | ||
| """ | ||
| rule = { | ||
| "PRIORITY": str(priority), | ||
| "PACKET_ACTION": "DROP" | ||
| } | ||
| if ip_ver(src_ip) == 4: | ||
| rule['ETHER_TYPE'] = str(ETHER_TYPE_IPV4) | ||
| rule['SRC_IP'] = src_ip | ||
| else: | ||
| rule['IP_TYPE'] = 'IPV6ANY' | ||
| rule['SRC_IPV6'] = src_ip | ||
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| return rule | ||
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| def get_rule(configdb, table_name, ip_prefix): | ||
| """ | ||
| Get Acl rule for given ip_prefix | ||
| """ | ||
| key_name = 'SRC_IP' if ip_ver(ip_prefix) == 4 else 'SRC_IPV6' | ||
| all_rules = get_all_acl_rules(configdb, table_name) | ||
| for key, rule in all_rules.items(): | ||
| if ip_prefix == rule.get(key_name, None): | ||
| if ip_prefix: | ||
| return {key: rule} | ||
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| return None | ||
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| def update_acl_table(configdb, acl_table_name, ip_prefix, action): | ||
| """ | ||
| Update ACL table to apply new rules for given ip_prefix. 'action' is supposed to be in ['DENY', 'ALLOW'] | ||
| For 'DENY', an 'DROP' rule for given ip_prefix will be added if not existed | ||
| For 'ALLOW', we will try to remove the existing 'DENY' rule, and nothing is changed if not existed | ||
| """ | ||
| confirm_required_table_existence(configdb, acl_table_name) | ||
| rule = get_rule(configdb, acl_table_name, ip_prefix) | ||
| rule_key = list(rule.keys())[0] if rule else None | ||
| rule_value = list(rule.values())[0] if rule else None | ||
| if action == ACTION_ALLOW: | ||
| if not rule: | ||
| return | ||
| # Delete existing BLOCK rule for given ip_prefix | ||
| # Pass None as data will delete the entry | ||
| configdb.mod_entry(CONFIG_DB_ACL_RULE_TABLE, rule_key, None) | ||
| else: | ||
| if rule: | ||
| if rule_value['PACKET_ACTION'] == 'DROP': | ||
| return | ||
| else: | ||
| # If there is 'FORWARDED' ACL rule, then change it to 'DROP' | ||
| rule_value['PACKET_ACTION'] = 'DROP' | ||
| configdb.mod_entry(CONFIG_DB_ACL_RULE_TABLE, rule_key, rule_value) | ||
| else: | ||
| priority = ACL_RULE_PRIORITY | ||
| new_rule_key = (acl_table_name, get_acl_rule_key(ip_prefix)) | ||
| new_rule_value = build_acl_rule(priority, ip_prefix) | ||
| configdb.set_entry(CONFIG_DB_ACL_RULE_TABLE, new_rule_key, new_rule_value) | ||
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| def list_all_null_route_rules(configdb, table_name): | ||
| """ | ||
| List all rules added by this script | ||
| """ | ||
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| confirm_required_table_existence(configdb, table_name) | ||
| header = ("Table", "Rule", "Priority", "Action", "Match") | ||
| all_rules = get_all_acl_rules(configdb, table_name) | ||
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| match_keys = ["SRC_IP", "SRC_IPV6"] | ||
| data = [] | ||
| for (_, rule_id), rule in all_rules.items(): | ||
| priority = rule.get("PRIORITY", "N/A") | ||
| action = rule.get("PACKET_ACTION", "N/A") | ||
| match = "N/A" | ||
| for k in match_keys: | ||
| if k in rule: | ||
| match = rule[k] | ||
| break | ||
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| data.append([table_name, rule_id, priority, action, match]) | ||
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| print(tabulate.tabulate(data, headers=header, tablefmt="simple", missingval="")) | ||
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| def null_route_helper(table_name, action, ip_prefix=None): | ||
| """ | ||
| Helper function called by 'click'. | ||
| """ | ||
| configdb = ConfigDBConnector() | ||
| configdb.connect() | ||
| if action == ACTION_LIST: | ||
| list_all_null_route_rules(configdb, table_name) | ||
| else: | ||
| ip_prefix = validate_input(ip_prefix) | ||
| update_acl_table(configdb, table_name, ip_prefix, action) | ||
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| @click.group() | ||
| def cli(): | ||
| pass | ||
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| # ./null_route_helper block table_name 1.2.3.4 | ||
| @cli.command('block') | ||
| @click.argument("table_name", type=click.STRING, required=True) | ||
| @click.argument("ip_prefix", type=click.STRING, required=True) | ||
| def block(table_name, ip_prefix): | ||
| """ | ||
| Block traffic from given src ip prefix | ||
| """ | ||
| null_route_helper(table_name, ACTION_DENY, ip_prefix) | ||
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| # ./null_route_helper unblock table_name 1.2.3.4 | ||
| @cli.command('unblock') | ||
| @click.argument("table_name", type=click.STRING, required=True) | ||
| @click.argument("ip_prefix", type=click.STRING, required=True) | ||
| def unblock(table_name, ip_prefix): | ||
| """ | ||
| Unblock traffic from given src ip prefix | ||
| """ | ||
| null_route_helper(table_name, ACTION_ALLOW, ip_prefix) | ||
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| # ./null_route_helper list table_name | ||
| @cli.command('list') | ||
| @click.argument("table_name", type=click.STRING, required=True) | ||
| def list_rules(table_name): | ||
| """ | ||
| List all rules *added by this script* | ||
| """ | ||
| null_route_helper(table_name, ACTION_LIST) | ||
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| if __name__ == "__main__": | ||
| cli() | ||
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