Hi,
comments inline.
> 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 <b...@einfach.org>
> ---
> net/isc-dhcp/files/dhcrelay4.init | 8 ++
> net/isc-dhcp/files/etc/config/dhcrelay | 3 +
> .../patches/100-relay-rfc3527-link-selection.patch | 100
> +++++++++++++++++++++
> 3 files changed, 111 insertions(+)
> create mode 100644
> net/isc-dhcp/patches/100-relay-rfc3527-link-selection.patch
>
> diff --git a/net/isc-dhcp/files/dhcrelay4.init
> b/net/isc-dhcp/files/dhcrelay4.init
> index 0f87b37..d03722f 100644
> --- a/net/isc-dhcp/files/dhcrelay4.init
> +++ b/net/isc-dhcp/files/dhcrelay4.init
> @@ -29,6 +29,14 @@ start() {
> done
> fi
>
> + # link selection sub-option (RFC3527)
> + local link_selection
> + config_get link_selection ipv4 link_selection
> + if [ -n "$link_selection" ]; then
> + config_get ifname "$link_selection" ifname
This relies on state vars which will get deprecated soon. Should be
converted to use "network_get_device" from /lib/functions/network.sh.
Example:
if network_get_device ifname "$link_selection"; then
append args "-l $ifname"
fi
> + 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 1b89782..b3b53b5 100644
> --- 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
> index 0000000..1f593ee
> --- /dev/null
> +++ b/net/isc-dhcp/patches/100-relay-rfc3527-link-selection.patch
Can you elaborate on the origin of this patch? Was it written by you?
> @@ -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) "
>
~ Jow
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