Attachment 7317 Details for Bug 34347 – Вариант решения, вовремя зачищающий маршрут из сабжа.

[patch] Вариант решения, вовремя зачищающий маршрут из сабжа.

0001-dhcp.c-Remove-temporary-default-route-properly.patch (text/plain), 2.81 KB, created by Arseny Maslennikov on 2017-12-15 00:08:04 MSK

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Creator: Arseny Maslennikov

Created: 2017-12-15 00:08:04 MSK

Size: 2.81 KB

patch

obsolete

>From b98780139c5f39dbd25e0118de165d90ddd1f13a Mon Sep 17 00:00:00 2001
>From: Arseny Maslennikov <arseny@altlinux.org>
>Date: Thu, 14 Dec 2017 16:21:28 +0300
>Subject: [PATCH] dhcp.c: Remove temporary default route properly
>MIME-Version: 1.0
>Content-Type: text/plain; charset=UTF-8
>Content-Transfer-Encoding: 8bit
>
>DHCP is implemented in propagator in a rather lazy way:
>to dynamically configure a network interface, say `eno1',
>instead of slinging raw Ethernet frames around like everyone else,
>it sets up a (temporary) default null route through that interface
>and throws UDP messages with actual bootp payload.
>
>`ip' utility describes such a route as `default dev eno1 scope link'
>
>The idea behind this presumably was to avoid generating IP and UDP
>headers manually while the null route is sufficient to send a couple of
>link-wide (maybe broadcast) messages and generic enough to work anywhere.
>
>To this date propagator didn't bother to remove that route,
>so *in some networks* it had persisted even after the initramfs
>(and propagator itself) was long gone, and in other networks did not,
>having been luckily replaced by the default route to DHCP gateway.
>
>In the cases where it did the real problem showed itself
>after the real userspace (for example, in a live distro)
>eventually tried to reconfigure the network (because why not?).
>The pesky null route was most often left untouched by the DHCP client
>(ALT live distros mostly use dhcpcd), managing to squeeze its way
>up the routing table and effectively preventing the host
>from network access beyond a router.
>
>If the NFS root is behind a couple routers, any attempt to access
>the file system gets stuck â the system keeps tirelessly looking for
>the NFS host via ARP.
>---
> dhcp.c | 32 ++++++++++++++++++++++++++++++++
> 1 file changed, 32 insertions(+)
>
>diff --git a/dhcp.c b/dhcp.c
>index 86e3a74..bb4a2d6 100644
>--- a/dhcp.c
>+++ b/dhcp.c
>@@ -228,6 +228,37 @@ static int initial_setup_interface(char * device, int s) {
> 	return 0;
> }
> 
>+static int interface_cleanup(char * device, int s) {
>+	/*
>+	 * Removing the auxiliary route
>+	 * made by initial_setup_interface()
>+	 */
>+	struct rtentry route;
>+	struct sockaddr_in* address;
>+
>+	memset(&route, 0, sizeof(route));
>+
>+	route.rt_dev = device;
>+	route.rt_flags = RTF_UP | RTF_GATEWAY;
>+	route.rt_metric = 0;
>+
>+	address = &route.rt_dst;
>+	address->sin_family = AF_INET;
>+
>+	address = &route.rt_gateway;
>+	address->sin_family = AF_INET;
>+
>+	address = &route.rt_genmask;
>+	address->sin_family = AF_INET;
>+
>+	if (ioctl(s, SIOCDELRT, &route)) {
>+		close(s);
>+		log_perror("SIOCDELRT");
>+		return -1;
>+	}
>+
>+	return 0;
>+}
> 
> void set_missing_ip_info(struct interface_info * intf)
> {
>@@ -669,6 +700,7 @@ enum return_type perform_dhcp(struct interface_info * intf)
> 	}
> 	lease = ntohl(lease);
> 
>+	interface_cleanup(intf->device, s);
> 	close(s);
> 	free(vendorClass);
> 
>-- 
>2.10.4
>

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