gcoap: Do not send responses from multicast addresses #19272
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chrysn
added
Type: bug
chrysn
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PeterKietzmann and
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benpicco
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Feb 13, 2023
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Thanks bors merge |
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Feb 13, 2023
18257: drivers/wdt: add periph_wdt_auto_start for early watchdog r=benpicco a=benpicco 19272: gcoap: Do not send responses from multicast addresses r=chrysn a=chrysn ### Contribution description Since #18026, CoAP requests to multicast addresses (eg. `ff02::1`) came back from that exact address, which Linux rightfully just drops. The fix uses the existing multicast check from #17978 (thanks `@benpicco` for making me write this as dedicated function, I just had to generalize it removing one struct layer), and foregoes setting the source address when responding to multicasts. ### Testing procedure * Run the gcoap example * Send a CoAP request to a multicast address RIOT listens to, eg. `./aiocoap-client coap://'[ff02::1%tapbr0]'/.well-known/core --non` Before, this got no response (while you see it arrive on wireshark). After, you get a correct response with two lines of note: ``` WARNING:coap:Sending request to multicast via unicast request method Response arrived from different address; base URI is coap://[fe80::3c63:beff:fe85:ca96%tapbr0]/.well-known/core ``` (The former is aiocoap telling us that we're not using the nonexistent multicast API so it's really more of an anycast, the latter is useful factual information). Co-authored-by: Benjamin Valentin <benjamin.valentin@ml-pa.com> Co-authored-by: chrysn <chrysn@fsfe.org>
OlegHahm
reviewed
Feb 13, 2023
| sock_udp_aux_tx_t aux_out = { | ||
| .flags = SOCK_AUX_SET_LOCAL, | ||
| .local = aux_in.local, | ||
| }; | ||
| if (_ep_is_multicast(&aux_in.local)) { | ||
| aux_out_ptr = NULL; |
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Probably I'm too late, but a comment about the semantics of setting this pointer to NULL here would have been nice.
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Good point, given it takes several indirections before this wins up in a function where one can read the documentation.
Comment added, let's see how mad bors will get at me for throwing logs before its merge train.
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Contribution description
Since #18026, CoAP requests to multicast addresses (eg.
ff02::1) came back from that exact address, which Linux rightfully just drops.The fix uses the existing multicast check from #17978 (thanks @benpicco for making me write this as dedicated function, I just had to generalize it removing one struct layer), and foregoes setting the source address when responding to multicasts.
Testing procedure
./aiocoap-client coap://'[ff02::1%tapbr0]'/.well-known/core --nonBefore, this got no response (while you see it arrive on wireshark). After, you get a correct response with two lines of note:
(The former is aiocoap telling us that we're not using the nonexistent multicast API so it's really more of an anycast, the latter is useful factual information).