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ipv4: Reject routes specifying ECN bits in rtm_tos

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Use the new dscp_t type to replace the fc_tos field of fib_config, to
ensure IPv4 routes aren't influenced by ECN bits when configured with
non-zero rtm_tos.

Before this patch, IPv4 routes specifying an rtm_tos with some of the
ECN bits set were accepted. However they wouldn't work (never match) as
IPv4 normally clears the ECN bits with IPTOS_RT_MASK before doing a FIB
lookup (although a few buggy code paths don't).

After this patch, IPv4 routes specifying an rtm_tos with any ECN bit
set is rejected.

Note: IPv6 routes ignore rtm_tos altogether, any rtm_tos is accepted,
but treated as if it were 0.

Signed-off-by: Guillaume Nault <gnault@redhat.com>
Acked-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Guillaume Nault
2022-02-04 14:58:16 +01:00
committed by Jakub Kicinski
parent 563f8e97e0
commit f55fbb6afb
4 changed files with 93 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
net/ipv4/fib_frontend.c
View File

@@ -32,6 +32,7 @@
#include <linux/list.h>
#include <linux/slab.h>
#include <net/inet_dscp.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
@@ -735,8 +736,16 @@ static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
memset(cfg, 0, sizeof(*cfg));
rtm = nlmsg_data(nlh);
if (!inet_validate_dscp(rtm->rtm_tos)) {
NL_SET_ERR_MSG(extack,
"Invalid dsfield (tos): ECN bits must be 0");
err = -EINVAL;
goto errout;
}
cfg->fc_dscp = inet_dsfield_to_dscp(rtm->rtm_tos);
cfg->fc_dst_len = rtm->rtm_dst_len;
cfg->fc_tos = rtm->rtm_tos;
cfg->fc_table = rtm->rtm_table;
cfg->fc_protocol = rtm->rtm_protocol;
cfg->fc_scope = rtm->rtm_scope;