gcoap: add remote sock_udp_ep_t to coap_request_ctx_t

[benpicco]

Contribution description

It can be useful to know over which interface a CoAP request was received.
(e.g. we have a device with two SLIP + power interfaces, both can be turned off and on individually. If a board registers with the central control board, we want to know to which interface it is connected so we know where to cut power.)

Testing procedure

Issues/PRs references

[benpicco]

This allows us to remove some warts introduced by the GCoAP forward proxy - and since the coap_request_ctx_t struct is completely internal, this isn't even an API change 😄

[fabian18]

If you do not intend to add local address information in this PR and murdock becomes green, I think this is ready to be merged.

Just some testing:

diff --git a/sys/net/application_layer/gcoap/fileserver.c b/sys/net/application_layer/gcoap/fileserver.c
index eaf14a252b..35c742816d 100644
--- a/sys/net/application_layer/gcoap/fileserver.c
+++ b/sys/net/application_layer/gcoap/fileserver.c
@@ -25,10 +25,12 @@
 #include "checksum/fletcher32.h"
 #include "net/gcoap/fileserver.h"
 #include "net/gcoap.h"
+#include "net/nanocoap.h"
+#include "net/sock/util.h"
 #include "vfs.h"
 #include "vfs_util.h"
 
-#define ENABLE_DEBUG 0
+#define ENABLE_DEBUG 1
 #include "debug.h"
 
 /** Maximum length of an expressible path, including the trailing 0 character. */
@@ -514,6 +516,16 @@ ssize_t gcoap_fileserver_handler(coap_pkt_t *pdu, uint8_t *buf, size_t len,
     const char *resource = coap_request_ctx_get_path(ctx);
     struct requestdata request = {0};
 
+    if (ENABLE_DEBUG) {
+        if (GCOAP_SOCKET_TYPE_UDP == coap_request_ctx_get_tl_type(ctx)) {
+            const sock_udp_ep_t *ep = coap_request_ctx_get_remote_udp(ctx);
+            char addr_str[] = "0000:0000:0000:0000:0000:0000:0000:0000";
+            uint16_t port;
+            sock_udp_ep_fmt(ep, addr_str, &port);
+            DEBUG("gcoap_fileserver: got a request from [%s]:%u\n", addr_str, port);
+        }
+    }
+
     /** Index in request.namebuf. Must not point at the last entry as that will be
      * zeroed to get a 0-terminated string. */
     size_t namelength = 0;

2022-09-11 14:36:46,131 # gcoap_fileserver: got a request from [fe80::3478:9157:9fd5:81c3%6]:34428

[benpicco]

If you do not intend to add local address information in this PR and murdock becomes green, I think this is ready to be merged.

I think this PR does enough already. We can add local address information in a follow-up.

[fabian18]

ACK

[benpicco]

Thank you for the review!