[201811][dhcp_relay] Add support for DHCP client(s) on one VLAN and DHCP server(s) on another #2919
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…on all upstream interfaces
… interface if it is a directed broadcast
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Retest this please. |
lguohan
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May 18, 2019
yxieca
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Aug 11, 2023
…atically (#16110) src/sonic-utilities * 0f001c56 - (HEAD -> 202205, origin/202205) UT change: for db_migrator test do not check for RESTAPI cert values (#2919) (4 hours ago) [Vaibhav Hemant Dixit] * 69d348d1 - [CLI][Show][BGP] Show BGP Change for no neighbor scenario (#2885) (6 hours ago) [Dev Ojha] * 4c6af3c3 - [multi-asic] Refine [override config table] for corner cases (#2918) (6 hours ago) [wenyiz2021] * bef3ffeb - [db_migrator] Set docker_routing_config_mode to the value obtained from minigraph parser (#2890) (#2922) (7 hours ago) [Vaibhav Hemant Dixit]
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Previously, the DHCP relay agent in SONiC would not relay DHCP requests to other VLANs. Therefore, if a DHCP client and the DHCP server it needed to communicate with resided on different VLANs under the same ToR device, the DHCP server would never receive the requests. The reason for this was because there was no way to specify whether the agent should only listen for requests or responses on each interface, so each DHCP relay agent could only listen on one VLAN to avoid sending DHCP requests and replies to incorrect DHCP servers.
How I did it
-idand-iuarguments, which allow us to specify 'downstream' and 'upstream' interfaces, respectively (the relay agent will only listen for requests on downstream interfaces, and will only listen for replies on upstream interfaces.-id), and all other interfaces (including all other VLAN interfaces) as upstream interfaces (-iu).ERR dhcrelay[172]: send_packet: Permission denied. I discovered that this was due to the relay agent being built by default to open one shared socket on a "fallback" interface, without theSO_BROADCASTflag set. I then added a patch to force the relay agent to open one socket per interface, each with theSO_BROADCASTflag set. I then noticed, however, that when built with this configuration, the relay agent would only relay packets on one upstream interface, so I created another patch, firstly fixing a bug that prevented a fallback interface from being created ifUSE_SOCKETSwas defined. With this fix, I was able to open sockets on all specified interfaces, as well as a fallback interface. Then I was able to create a patch to relay request packets as follows: