[Dnsmasq-discuss] [PATCH] DHCPv6: Honor assigning IPv6 address based on MAC address

Pali Rohár pali.rohar at gmail.com
Fri Jan 11 16:52:43 GMT 2019


Hello, can somebody look at this patch?

I remember that more people asked for ability to assign IPv6 address
based on MAC address specified in config file, rather then IAID/DUID.

On Monday 17 December 2018 18:41:09 Pali Rohár wrote:
> Currently IPv6 addresses are assigned to tuple (IAID, DUID). When system
> changes IAID/DUID then old assigned IPv6 address cannot be reused, even
> when in config file was DHCPv6 assignment based on MAC address (and not on
> DUID).
> 
> IAID/DUID is changed when rebooting from one operating system to another;
> or after reinstalling system. In reality it is normal that DUID of some
> machine is changed, so people rather assign also IPv6 addresses based on
> MAC address.
> 
> So assigning IPv6 based on MAC address in dnsmasq is currently semi-broken.
> 
> This patch tries to fix it and honors IPv6 config rules with MAC address,
> to always assign particular IPv6 address to specific MAC address (when
> configured). And ignores the fact if IAID/DUID was changed.
> 
> Normally IPv6 address should be assigned by IAID/DUID (which also state
> DHCPv6 RFCs), but dnsmasq has already some support for assigning IPv6
> address based on MAC address, when users configured in config file.
> 
> So this patch just tries to fix above problem for user configuration with
> MAC addresses. It does not change assignment based on DUID.
> 
> Also this patch adds support for allowing IPv6 address to be associated
> with multiple hardware addresses, and gives dnsmasq permission to abandon a
> lease. This is similar functionality as already supported for IPv4 address.
> ---
>  man/dnsmasq.8 |  9 ++++++---
>  src/rfc3315.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++---------
>  2 files changed, 59 insertions(+), 12 deletions(-)
> 
> diff --git a/man/dnsmasq.8 b/man/dnsmasq.8
> index f01a5ba..8614f08 100644
> --- a/man/dnsmasq.8
> +++ b/man/dnsmasq.8
> @@ -1068,10 +1068,13 @@ will only match a
>  Token-Ring hardware address, since the ARP-address type for token ring
>  is 6. 
>  
> -As a special case, in DHCPv4, it is possible to include more than one
> -hardware address. eg:
> +It is possible to include more than one hardware address. eg for IPv4:
>  .B --dhcp-host=11:22:33:44:55:66,12:34:56:78:90:12,192.168.0.2
> -This allows an IP address to be associated with
> +or for IPv6:
> +.B --dhcp-host=11:22:33:44:55:66,12:34:56:78:90:12,[::2]
> +or for both:
> +.B --dhcp-host=11:22:33:44:55:66,12:34:56:78:90:12,192.168.0.2,[::2]
> +This allows an IPv4 and/or IPv6 address to be associated with
>  multiple hardware addresses, and gives dnsmasq permission to abandon a
>  DHCP lease to one of the hardware addresses when another one asks for
>  a lease. Beware that this is a dangerous thing to do, it will only
> diff --git a/src/rfc3315.c b/src/rfc3315.c
> index a20776d..c83cf2d 100644
> --- a/src/rfc3315.c
> +++ b/src/rfc3315.c
> @@ -54,7 +54,7 @@ static struct prefix_class *prefix_class_from_context(struct dhcp_context *conte
>  #endif
>  static void mark_context_used(struct state *state, struct in6_addr *addr);
>  static void mark_config_used(struct dhcp_context *context, struct in6_addr *addr);
> -static int check_address(struct state *state, struct in6_addr *addr);
> +static int check_address(struct state *state, struct dhcp_config *config, struct in6_addr *addr);
>  static void add_address(struct state *state, struct dhcp_context *context, unsigned int lease_time, void *ia_option, 
>  			unsigned int *min_time, struct in6_addr *addr, time_t now);
>  static void update_leases(struct state *state, struct dhcp_context *context, struct in6_addr *addr, unsigned int lease_time, time_t now);
> @@ -746,7 +746,7 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
>  		    /* If the client asks for an address on the same network as a configured address, 
>  		       offer the configured address instead, to make moving to newly-configured
>  		       addresses automatic. */
> -		    if (!(c->flags & CONTEXT_CONF_USED) && config_valid(config, c, &addr) && check_address(state, &addr))
> +		    if (!(c->flags & CONTEXT_CONF_USED) && config_valid(config, c, &addr) && check_address(state, config, &addr))
>  		      {
>  			req_addr = addr;
>  			mark_config_used(c, &addr);
> @@ -755,8 +755,14 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
>  		      }
>  		    else if (!(c = address6_available(state->context, &req_addr, solicit_tags, plain_range)))
>  		      continue; /* not an address we're allowed */
> -		    else if (!check_address(state, &req_addr))
> +		    else if (!check_address(state, config, &req_addr))
>  		      continue; /* address leased elsewhere */
> +		    else if (state->mac_len && config &&
> +			     config_has_mac(config, state->mac, state->mac_len, state->mac_type) &&
> +			     match_netid(c->filter, solicit_tags, plain_range) &&
> +			     config_valid(config, c, &addr) &&
> +			     !IN6_ARE_ADDR_EQUAL(&req_addr, &addr))
> +		      continue; /* another static address is configured */
>  		    
>  		    /* add address to output packet */
>  #ifdef OPTION6_PREFIX_CLASS
> @@ -772,10 +778,13 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
>  	    
>  	    /* Suggest configured address(es) */
>  	    for (c = state->context; c; c = c->current) 
> -	      if (!(c->flags & CONTEXT_CONF_USED) &&
> +	      if ((!(c->flags & CONTEXT_CONF_USED) ||
> +		   (state->mac_len && config &&
> +		    config_has_mac(config, state->mac, state->mac_len, state->mac_type)
> +		   )) &&
>  		  match_netid(c->filter, solicit_tags, plain_range) &&
>  		  config_valid(config, c, &addr) && 
> -		  check_address(state, &addr))
> +		  check_address(state, config, &addr))
>  		{
>  		  mark_config_used(state->context, &addr);
>  		  if (have_config(config, CONFIG_TIME))
> @@ -800,6 +809,12 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
>  		req_addr = ltmp->addr6;
>  		if ((c = address6_available(state->context, &req_addr, solicit_tags, plain_range)))
>  		  {
> +		    if (state->mac_len && config &&
> +			config_has_mac(config, state->mac, state->mac_len, state->mac_type) &&
> +			match_netid(c->filter, solicit_tags, plain_range) &&
> +			config_valid(config, c, &addr) &&
> +			!IN6_ARE_ADDR_EQUAL(&req_addr, &addr))
> +		      continue; /* skip this lease because another static address is configured */
>  #ifdef OPTION6_PREFIX_CLASS
>  		    if (dump_all_prefix_classes && state->ia_type == OPTION6_IA_NA)
>  		      state->send_prefix_class = prefix_class_from_context(c);
> @@ -943,7 +958,7 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
>  			put_opt6_string(_("address unavailable"));
>  			end_opt6(o1);
>  		      }
> -		    else if (!check_address(state, &req_addr))
> +		    else if (!check_address(state, config, &req_addr))
>  		      {
>  			/* Address leased to another DUID/IAID */
>  			o1 = new_opt6(OPTION6_STATUS_CODE);
> @@ -1064,6 +1079,17 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
>  		    struct in6_addr addr;
>  		    unsigned int lease_time;
>  
> +		    /* check if another static address is preferred */
> +		    if (state->mac_len && config &&
> +		        config_has_mac(config, state->mac, state->mac_len, state->mac_type) &&
> +		        config_valid(config, this_context, &addr) &&
> +		        !IN6_ARE_ADDR_EQUAL(&req_addr, &addr))
> +		      {
> +			preferred_time = valid_time = 0;
> +			message = _("deprecated");
> +		      }
> +		    else
> +		      {
>  		    get_context_tag(state, this_context);
>  		    
>  		    if (config_valid(config, this_context, &addr) && IN6_ARE_ADDR_EQUAL(&addr, &req_addr) && have_config(config, CONFIG_TIME))
> @@ -1089,6 +1115,7 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
>  		    
>  		    if (preferred_time == 0)
>  		      message = _("deprecated");
> +		      }
>  		  }
>  		else
>  		  {
> @@ -1135,11 +1162,24 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
>  		 ia_option = opt6_find(opt6_next(ia_option, ia_end), ia_end, OPTION6_IAADDR, 24))
>  	      {
>  		struct in6_addr req_addr;
> +		struct in6_addr addr;
> +		struct dhcp_context *c;
> +		int config_addr_ok = 1;
>  
>  		/* alignment */
>  		memcpy(&req_addr, opt6_ptr(ia_option, 0), IN6ADDRSZ);
> +
> +		c = address6_valid(state->context, &req_addr, tagif, 1);
> +
> +		if (c && state->mac_len && config &&
> +		    config_has_mac(config, state->mac, state->mac_len, state->mac_type) &&
> +		    config_valid(config, c, &addr) &&
> +		    !IN6_ARE_ADDR_EQUAL(&req_addr, &addr))
> +		  {
> +		    config_addr_ok = 0;
> +		  }
>  		
> -		if (!address6_valid(state->context, &req_addr, tagif, 1))
> +		if (!c || !config_addr_ok)
>  		  {
>  		    o1 = new_opt6(OPTION6_STATUS_CODE);
>  		    put_opt6_short(DHCP6NOTONLINK);
> @@ -1772,11 +1812,15 @@ static void mark_config_used(struct dhcp_context *context, struct in6_addr *addr
>        context->flags |= CONTEXT_CONF_USED;
>  }
>  
> -/* make sure address not leased to another CLID/IAID */
> -static int check_address(struct state *state, struct in6_addr *addr)
> +/* check that ipv6 address belongs to config with same mac address as in state or ipv6 address is not leased to another CLID/IAID */
> +static int check_address(struct state *state, struct dhcp_config *config, struct in6_addr *addr)
>  { 
>    struct dhcp_lease *lease;
>  
> +  if (state->mac_len && config &&
> +      config_has_mac(config, state->mac, state->mac_len, state->mac_type))
> +    return 1;
> +
>    if (!(lease = lease6_find_by_addr(addr, 128, 0)))
>      return 1;
>  

-- 
Pali Rohár
pali.rohar at gmail.com
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