gnu: ucx: Restore (and adapt) ioctl fallback patch.

This is a followup to 4ebd4a58ce which
removed the patch, but it was still necessary for some dependents.

* gnu/packages/patches/ucx-tcp-iface-ioctl.patch: New file.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/fabric-management.scm (ucx)[source](patches): New field.

gnu/local.mk

@@ -1744,6 +1744,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/twinkle-bcg729.patch			\
   %D%/packages/patches/u-boot-rockchip-inno-usb.patch		\
   %D%/packages/patches/u-boot-riscv64-fix-extlinux.patch	\
+  %D%/packages/patches/ucx-tcp-iface-ioctl.patch		\
   %D%/packages/patches/udiskie-no-appindicator.patch		\
   %D%/packages/patches/ungoogled-chromium-extension-search-path.patch	\
   %D%/packages/patches/unison-fix-ocaml-4.08.patch		\

gnu/packages/fabric-management.scm

@@ -188,6 +188,7 @@ (define-public ucx
                     (url "https://github.com/openucx/ucx")
                     (commit (string-append "v" version))))
               (file-name (git-file-name name version))
+              (patches (search-patches "ucx-tcp-iface-ioctl.patch"))
               (sha256
                (base32
                 "0i0ji5ivzxjqh3ys1m517ghw3am7cw1hvf40ma7hsq3wznsyx5s1"))))

gnu/packages/patches/ucx-tcp-iface-ioctl.patch

@@ -0,0 +1,108 @@
+Since /sys is unavailable in build environments, the list of available
+TCP network interfaces cannot be obtained via /sys/class/net.  This patch
+provides alternative code that uses the SIOCGIFCONF ioctl to get the
+names of the available TCP network interfaces.
+
+diff --git a/src/uct/tcp/tcp_iface.c b/src/uct/tcp/tcp_iface.c
+index cad4a2709..7c1d2c9de 100644
+--- a/src/uct/tcp/tcp_iface.c
++++ b/src/uct/tcp/tcp_iface.c
+@@ -17,6 +17,8 @@
+ #include <sys/poll.h>
+ #include <netinet/tcp.h>
+ #include <dirent.h>
++#include <net/if.h>
++#include <sys/ioctl.h>
+ 
+ 
+ extern ucs_class_t UCS_CLASS_DECL_NAME(uct_tcp_iface_t);
+@@ -586,6 +588,68 @@ static UCS_CLASS_DEFINE_NEW_FUNC(uct_tcp_iface_t, uct_iface_t, uct_md_h,
+                                  uct_worker_h, const uct_iface_params_t*,
+                                  const uct_iface_config_t*);
+ 
++/* Fetch information about available network devices through an ioctl.  */
++static ucs_status_t query_devices_ioctl(uct_md_h md,
++					uct_tl_device_resource_t **tl_devices_p,
++					unsigned *num_tl_devices_p)
++{
++    int sock, err, i;
++    uct_tl_device_resource_t *resources, *tmp;
++    unsigned num_resources;
++    ucs_status_t status;
++    struct ifconf conf;
++    struct ifreq reqs[10];
++
++    conf.ifc_len = sizeof reqs;
++    conf.ifc_req = reqs;
++
++    sock = socket(SOCK_STREAM, AF_INET, 0);
++    if (sock < 0) {
++	ucs_error("socket(2) failed: %m");
++	status = UCS_ERR_IO_ERROR;
++	goto out;
++    }
++
++    err = ioctl(sock, SIOCGIFCONF, &conf);
++    if (err < 0) {
++	ucs_error("SIOCGIFCONF ioctl failed: %m");
++	status = UCS_ERR_IO_ERROR;
++	goto out;
++    }
++
++    resources     = NULL;
++    num_resources = 0;
++    for (i = 0; i < conf.ifc_len / sizeof(struct ifreq); i++) {
++	const char *name = reqs[i].ifr_name;
++
++        if (!ucs_netif_is_active(name)) {
++            continue;
++        }
++
++        tmp = ucs_realloc(resources, sizeof(*resources) * (num_resources + 1),
++                          "tcp resources");
++        if (tmp == NULL) {
++            ucs_free(resources);
++            status = UCS_ERR_NO_MEMORY;
++            goto out;
++        }
++        resources = tmp;
++
++        ucs_snprintf_zero(resources[i].name, sizeof(resources[i].name),
++                          "%s", name);
++        resources[i].type = UCT_DEVICE_TYPE_NET;
++        ++num_resources;
++    }
++
++    *num_tl_devices_p = num_resources;
++    *tl_devices_p     = resources;
++    status            = UCS_OK;
++
++out:
++    if (sock >= 0) close(sock);
++    return status;
++}
++
+ ucs_status_t uct_tcp_query_devices(uct_md_h md,
+                                    uct_tl_device_resource_t **devices_p,
+                                    unsigned *num_devices_p)
+@@ -599,9 +663,9 @@ ucs_status_t uct_tcp_query_devices(uct_md_h md,
+ 
+     dir = opendir(netdev_dir);
+     if (dir == NULL) {
+-        ucs_error("opendir(%s) failed: %m", netdev_dir);
+-        status = UCS_ERR_IO_ERROR;
+-        goto out;
++	/* When /sys is unavailable, as can be the case in a container,
++	 * resort to a good old 'ioctl'.  */
++	return query_devices_ioctl(md, devices_p, num_devices_p);
+     }
+ 
+     devices     = NULL;
+@@ -655,7 +719,6 @@ ucs_status_t uct_tcp_query_devices(uct_md_h md,
+ 
+ out_closedir:
+     closedir(dir);
+-out:
+     return status;
+ }
+