isc-dhcp: dhcrelay: Add RFC3527 link selection sub-option

RFC3527 link selection sub-option is used to select the "uplink" interface of
dhcrelay in cases where the DHCP server does not know how to reach the dhcrelay
based on the DHCP range. This can happen in weird network configurations like
Mesh networks.

Signed-off-by: Bruno Randolf <br1@einfach.org>
SVN-Revision: 38447

diff --git a/net/isc-dhcp/files/dhcrelay4.init b/net/isc-dhcp/files/dhcrelay4.init
index e1e68711e83036a907720b320f50cd5e90da229d..9af0f84e1baaa168c1cd98ce70c8141b9c2344c9 100644 (file)
--- a/net/isc-dhcp/files/dhcrelay4.init
+++ b/net/isc-dhcp/files/dhcrelay4.init
@@ -26,6 +26,13 @@ start() {
                fi
        done
 
+       # link selection sub-option (RFC3527)
+       local link_selection
+       config_get link_selection ipv4 link_selection
+       if network_get_device ifname "$link_selection"; then
+               append args "-l $ifname"
+       fi
+
        # relay mode
        local relay_mode
        config_get relay_mode ipv4 relay_mode

diff --git a/net/isc-dhcp/files/etc/config/dhcrelay b/net/isc-dhcp/files/etc/config/dhcrelay
index 1b89782569358870f75415d7420dc6efc2b3e793..b3b53b516780e4bc7b2744d95e676e5b852b80fc 100644 (file)
--- a/net/isc-dhcp/files/etc/config/dhcrelay
+++ b/net/isc-dhcp/files/etc/config/dhcrelay
@@ -15,6 +15,9 @@ config dhcrelay ipv4
        # 'discard': Don't forward
        option 'relay_mode' ''
 
+       # enable RFC3527 link selection sub-option and use the IP address of
+       # the specified network interface as "uplink" IP address (e.g. wan)
+       option 'link_selection' ''
 
 config dhcrelay ipv6
 #      option dhcpserver '2001:db8:1::1'

diff --git a/net/isc-dhcp/patches/100-relay-rfc3527-link-selection.patch b/net/isc-dhcp/patches/100-relay-rfc3527-link-selection.patch
new file mode 100644 (file)
index 0000000..1f593ee
--- /dev/null
+++ b/net/isc-dhcp/patches/100-relay-rfc3527-link-selection.patch
@@ -0,0 +1,100 @@
+--- a/relay/dhcrelay.c
++++ b/relay/dhcrelay.c
+@@ -65,6 +65,7 @@ int server_packets_relayed = 0;      /* Packe
+ int client_packet_errors = 0; /* Errors sending packets to clients. */
+ 
+ int add_agent_options = 0;    /* If nonzero, add relay agent options. */
++int add_rfc3527_suboption = 0;        /* If nonzero, add RFC3527 link selection sub-option. */
+ 
+ int agent_option_errors = 0;    /* Number of packets forwarded without
+                                  agent options because there was no room. */
+@@ -104,6 +105,8 @@ struct server_list {
+       struct sockaddr_in to;
+ } *servers;
+ 
++struct interface_info *uplink;
++
+ #ifdef DHCPv6
+ struct stream_list {
+       struct stream_list *next;
+@@ -144,6 +147,7 @@ static const char url[] =
+ "                     [-pf <pid-file>] [--no-pid]\n"\
+ "                     [-m append|replace|forward|discard]\n" \
+ "                     [-i interface0 [ ... -i interfaceN]\n" \
++"                     [-l interface]\n" \
+ "                     server0 [ ... serverN]\n\n" \
+ "       dhcrelay -6   [-d] [-q] [-I] [-c <hops>] [-p <port>]\n" \
+ "                     [-pf <pid-file>] [--no-pid]\n"\
+@@ -157,6 +161,7 @@ static const char url[] =
+ "                [-pf <pid-file>] [--no-pid]\n"\
+ "                [-m append|replace|forward|discard]\n" \
+ "                [-i interface0 [ ... -i interfaceN]\n" \
++"                [-l interface]\n" \
+ "                server0 [ ... serverN]\n\n"
+ #endif
+ 
+@@ -314,6 +319,20 @@ main(int argc, char **argv) {
+                               agent_relay_mode = discard;
+                       } else
+                               usage();
++              } else if (!strcmp (argv [i], "-l")) {
++                      add_agent_options = 1;
++                      add_rfc3527_suboption = 1;
++                      if (++i == argc)
++                              usage();
++
++                      status = interface_allocate(&uplink, MDL);
++                      if (status != ISC_R_SUCCESS)
++                              log_fatal("%s: interface_allocate: %s",
++                                        argv[i],
++                                        isc_result_totext(status));
++                      strcpy(uplink->name, argv[i]);
++                      interface_snorf(uplink, INTERFACE_REQUESTED);
++                      //interface_dereference(&uplink, MDL);
+               } else if (!strcmp(argv[i], "-D")) {
+ #ifdef DHCPv6
+                       if (local_family_set && (local_family == AF_INET6)) {
+@@ -685,12 +704,17 @@ do_relay4(struct interface_info *ip, str
+                                              ip->addresses[0])))
+               return;
+ 
++      /* RFC3527: Replace giaddr address by uplink address. The original
++       * giaddr will be used in the link selection sub-option */
++      if (add_rfc3527_suboption)
++              packet->giaddr = uplink->addresses[0];
++
+       /* If giaddr is not already set, Set it so the server can
+          figure out what net it's from and so that we can later
+          forward the response to the correct net.    If it's already
+          set, the response will be sent directly to the relay agent
+          that set giaddr, so we won't see it. */
+-      if (!packet->giaddr.s_addr)
++      else if (!packet->giaddr.s_addr)
+               packet->giaddr = ip->addresses[0];
+       if (packet->hops < max_hop_count)
+               packet->hops = packet->hops + 1;
+@@ -1062,6 +1086,9 @@ add_relay_agent_options(struct interface
+               optlen += ip->remote_id_len + 2;    /* RAI_REMOTE_ID + len */
+       }
+ 
++      if (add_rfc3527_suboption)
++              optlen += 6;
++
+       /* We do not support relay option fragmenting(multiple options to
+        * support an option data exceeding 255 bytes).
+        */
+@@ -1093,6 +1120,14 @@ add_relay_agent_options(struct interface
+                       memcpy(sp, ip->remote_id, ip->remote_id_len);
+                       sp += ip->remote_id_len;
+               }
++
++              if (add_rfc3527_suboption) {
++                      *sp++ = RAI_LINK_SELECT;
++                      *sp++ = 4u;
++                      memcpy(sp, &giaddr.s_addr, 4);
++                      sp += 4;
++                      log_debug ("RFC3527 link selection sub-option added: %s", inet_ntoa(giaddr));
++              }
+       } else {
+               ++agent_option_errors;
+               log_error("No room in packet (used %d of %d) "