syscalls: Add 'add-network-route/gateway' and 'delete-network-route'.

* guix/build/syscalls.scm (SIOCADDRT, SIOCDELRT): New variables.
(%rtentry): New C struct.
(RTF_UP, RTF_GATEWAY, %sockaddr-any): New variables.
(add-network-route/gateway, delete-network-route): New procedures.
* tests/syscalls.scm ("add-network-route/gateway")
("delete-network-route"): New tests.

2 files changed, 134 insertions, 0 deletions

diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index 85de47d26e..9386c0f5d0 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -95,6 +95,8 @@
             set-network-interface-netmask
             set-network-interface-up
             configure-network-interface
+            add-network-route/gateway
+            delete-network-route
 
             interface?
             interface-name
@@ -805,6 +807,14 @@ exception if it's already taken."
   (if (string-contains %host-type "linux")
       #x891c                                      ;GNU/Linux
       -1))                                        ;FIXME: GNU/Hurd?
+(define SIOCADDRT
+  (if (string-contains %host-type "linux")
+      #x890B                                      ;GNU/Linux
+      -1))                                        ;FIXME: GNU/Hurd?
+(define SIOCDELRT
+  (if (string-contains %host-type "linux")
+      #x890C                                      ;GNU/Linux
+      -1))                                        ;FIXME: GNU/Hurd?
 
 ;; Flags and constants from <net/if.h>.
 
@@ -1090,6 +1100,106 @@ is true, it must be a socket address to use as the network mask."
 
 
 ;;;
+;;; Network routes.
+;;;
+
+(define-c-struct %rtentry                 ;'struct rtentry' from <net/route.h>
+  sizeof-rtentry
+  list
+  read-rtentry
+  write-rtentry!
+  (pad1            unsigned-long)
+  (destination     (array uint8 16))              ;struct sockaddr
+  (gateway         (array uint8 16))              ;struct sockaddr
+  (genmask         (array uint8 16))              ;struct sockaddr
+  (flags           unsigned-short)
+  (pad2            short)
+  (pad3            long)
+  (tos             uint8)
+  (class           uint8)
+  (pad4            (array uint8 (if (= 8 (sizeof* '*)) 3 1)))
+  (metric          short)
+  (device          '*)
+  (mtu             unsigned-long)
+  (window          unsigned-long)
+  (initial-rtt     unsigned-short))
+
+(define RTF_UP #x0001)                     ;'rtentry' flags from <net/route.h>
+(define RTF_GATEWAY #x0002)
+
+(define %sockaddr-any
+  (make-socket-address AF_INET INADDR_ANY 0))
+
+(define add-network-route/gateway
+  ;; To allow field names to be matched as literals, we need to move them out
+  ;; of the lambda's body since the parameters have the same name.  A lot of
+  ;; fuss for very little.
+  (let-syntax ((gateway-offset (identifier-syntax
+                                (c-struct-field-offset %rtentry gateway)))
+               (destination-offset (identifier-syntax
+                                    (c-struct-field-offset %rtentry destination)))
+               (genmask-offset (identifier-syntax
+                                (c-struct-field-offset %rtentry genmask))))
+    (lambda* (socket gateway
+                     #:key (destination %sockaddr-any) (genmask %sockaddr-any))
+      "Add a network route for DESTINATION (a socket address as returned by
+'make-socket-address') that goes through GATEWAY (a socket address).  For
+instance, the call:
+
+  (add-network-route/gateway sock
+                             (make-socket-address
+                               AF_INET
+                               (inet-pton AF_INET \"192.168.0.1\")
+                               0))
+
+is equivalent to this 'net-tools' command:
+
+  route add -net default gw 192.168.0.1
+
+because the default value of DESTINATION is \"0.0.0.0\"."
+      (let ((route (make-bytevector sizeof-rtentry 0)))
+        (write-socket-address! gateway route gateway-offset)
+        (write-socket-address! destination route destination-offset)
+        (write-socket-address! genmask route genmask-offset)
+        (bytevector-u16-native-set! route
+                                    (c-struct-field-offset %rtentry flags)
+                                    (logior RTF_UP RTF_GATEWAY))
+        (let-values (((ret err)
+                      (%ioctl (fileno socket) SIOCADDRT
+                              (bytevector->pointer route))))
+          (unless (zero? ret)
+            (throw 'system-error "add-network-route/gateway"
+                   "add-network-route/gateway: ~A"
+                   (list (strerror err))
+                   (list err))))))))
+
+(define delete-network-route
+  (let-syntax ((destination-offset (identifier-syntax
+                                    (c-struct-field-offset %rtentry destination))))
+    (lambda* (socket destination)
+      "Delete the network route for DESTINATION.  For instance, the call:
+
+  (delete-network-route sock
+                        (make-socket-address AF_INET INADDR_ANY 0))
+
+is equivalent to the 'net-tools' command:
+
+  route del -net default
+"
+
+      (let ((route (make-bytevector sizeof-rtentry 0)))
+        (write-socket-address! destination route destination-offset)
+        (let-values (((ret err)
+                      (%ioctl (fileno socket) SIOCDELRT
+                              (bytevector->pointer route))))
+          (unless (zero? ret)
+            (throw 'system-error "delete-network-route"
+                   "delete-network-route: ~A"
+                   (list (strerror err))
+                   (list err))))))))
+
+
+;;;
 ;;; Details about network interfaces---aka. 'getifaddrs'.
 ;;;
 
diff --git a/tests/syscalls.scm b/tests/syscalls.scm
index fd177265f0..e4ef32c522 100644
--- a/tests/syscalls.scm
+++ b/tests/syscalls.scm
@@ -374,6 +374,30 @@
              (#f #f)
              (lo (interface-address lo)))))))
 
+(test-skip (if (zero? (getuid)) 1 0))
+(test-assert "add-network-route/gateway"
+  (let ((sock    (socket AF_INET SOCK_STREAM 0))
+        (gateway (make-socket-address AF_INET
+                                      (inet-pton AF_INET "192.168.0.1")
+                                      0)))
+    (catch 'system-error
+      (lambda ()
+        (add-network-route/gateway sock gateway))
+      (lambda args
+        (close-port sock)
+        (memv (system-error-errno args) (list EPERM EACCES))))))
+
+(test-skip (if (zero? (getuid)) 1 0))
+(test-assert "delete-network-route"
+  (let ((sock        (socket AF_INET SOCK_STREAM 0))
+        (destination (make-socket-address AF_INET INADDR_ANY 0)))
+    (catch 'system-error
+      (lambda ()
+        (delete-network-route sock destination))
+      (lambda args
+        (close-port sock)
+        (memv (system-error-errno args) (list EPERM EACCES))))))
+
 (test-equal "tcgetattr ENOTTY"
   ENOTTY
   (catch 'system-error