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-rw-r--r--guix/build/syscalls.scm67
-rw-r--r--tests/syscalls.scm8
2 files changed, 73 insertions, 2 deletions
diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index 7a1bad7331..cd2797219f 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -30,7 +30,8 @@
MS_MOVE
mount
umount
- processes))
+ processes
+ network-interfaces))
;;; Commentary:
;;;
@@ -180,4 +181,68 @@ user-land process."
(scandir "/proc"))
<))
+
+;;;
+;;; Network interfaces.
+;;;
+
+(define SIOCGIFCONF ;from <bits/ioctls.h>
+ (if (string-contains %host-type "linux")
+ #x8912 ;GNU/Linux
+ #xf00801a4)) ;GNU/Hurd
+
+(define ifconf-struct
+ ;; 'struct ifconf', from <net/if.h>.
+ (list int ;int ifc_len
+ '*)) ;struct ifreq *ifc_ifcu
+
+(define ifreq-struct-size
+ ;; 'struct ifreq' begins with a char array containing the interface name,
+ ;; followed by a bunch of stuff. This is its size in bytes.
+ (if (= 8 (sizeof '*))
+ 40
+ 32))
+
+(define %ioctl
+ ;; The most terrible interface, live from Scheme.
+ (pointer->procedure int
+ (dynamic-func "ioctl" (dynamic-link))
+ (list int unsigned-long '*)))
+
+(define (bytevector->string-list bv stride len)
+ "Return the null-terminated strings found in BV every STRIDE bytes. Read at
+most LEN bytes from BV."
+ (let loop ((bytes (take (bytevector->u8-list bv)
+ (min len (bytevector-length bv))))
+ (result '()))
+ (match bytes
+ (()
+ (reverse result))
+ (_
+ (loop (drop bytes stride)
+ (cons (list->string (map integer->char
+ (take-while (negate zero?) bytes)))
+ result))))))
+
+(define* (network-interfaces #:optional sock)
+ "Return the list of existing network interfaces."
+ (let* ((close? (not sock))
+ (sock (or sock (socket SOCK_STREAM AF_INET 0)))
+ (len (* ifreq-struct-size 10))
+ (reqs (make-bytevector len))
+ (conf (make-c-struct ifconf-struct
+ (list len (bytevector->pointer reqs))))
+ (ret (%ioctl (fileno sock) SIOCGIFCONF conf))
+ (err (errno)))
+ (when close?
+ (close-port sock))
+ (if (zero? ret)
+ (bytevector->string-list reqs ifreq-struct-size
+ (match (parse-c-struct conf ifconf-struct)
+ ((len . _) len)))
+ (throw 'system-error "network-interface-list"
+ "network-interface-list: ~A"
+ (list (strerror err))
+ (list err)))))
+
;;; syscalls.scm ends here
diff --git a/tests/syscalls.scm b/tests/syscalls.scm
index ab34fc825b..fa6b67bf39 100644
--- a/tests/syscalls.scm
+++ b/tests/syscalls.scm
@@ -18,7 +18,8 @@
(define-module (test-syscalls)
#:use-module (guix build syscalls)
- #:use-module (srfi srfi-64))
+ #:use-module (srfi srfi-64)
+ #:use-module (ice-9 match))
;; Test the (guix build syscalls) module, although there's not much that can
;; actually be tested without being root.
@@ -42,6 +43,11 @@
;; Both return values have been encountered in the wild.
(memv (system-error-errno args) (list EPERM ENOENT)))))
+(test-assert "network-interfaces"
+ (match (network-interfaces)
+ (((? string? names) ..1)
+ (member "lo" names))))
+
(test-end)