[bug#27570] [PATCH v3] syscalls: Add network-interface-running?

[Danny Milosavljevic <dannym@scratchpost.org>]

* guix/build/syscalls.scm (network-interface-running?): New variable.
Export it.
---
 guix/build/syscalls.scm | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index 9c082b435..5a6662afe 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -88,6 +88,7 @@
 
             PF_PACKET
             AF_PACKET
+            network-interface-running?
             all-network-interface-names
             network-interface-names
             network-interface-netmask
@@ -1108,6 +1109,7 @@ bytes."
 (define-as-needed IFF_UP #x1)                     ;Interface is up
 (define-as-needed IFF_BROADCAST #x2)              ;Broadcast address valid.
 (define-as-needed IFF_LOOPBACK #x8)               ;Is a loopback net.
+(define-as-needed IFF_RUNNING #x40)               ;interface RFC2863 OPER_UP
 
 (define IF_NAMESIZE 16)                           ;maximum interface name size
 
@@ -1282,6 +1284,13 @@ interface NAME."
     (close-port sock)
     (not (zero? (logand flags IFF_LOOPBACK)))))
 
+(define (network-interface-running? name)
+  "Return true if NAME designates a running network interface."
+  (let* ((sock  (socket SOCK_STREAM AF_INET 0))
+         (flags (network-interface-flags sock name)))
+    (close-port sock)
+    (not (zero? (logand flags IFF_RUNNING)))))
+
 (define-as-needed (set-network-interface-flags socket name flags)
   "Set the flag of network interface NAME to FLAGS."
   (let ((req (make-bytevector ifreq-struct-size)))