bpf: Unmask upper DSCP bits in bpf_fib_lookup() helper

The helper performs a FIB lookup according to the parameters in the
'params' argument, one of which is 'tos'. According to the test in
test_tc_neigh_fib.c, it seems that BPF programs are expected to
initialize the 'tos' field to the full 8 bit DS field from the IPv4
header.

Unmask the upper DSCP bits before invoking the IPv4 FIB lookup APIs so
that in the future the lookup could be performed according to the full
DSCP value.

No functional changes intended since the upper DSCP bits are masked when
comparing against the TOS selectors in FIB rules and routes.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Acked-by: Florian Westphal <fw@strlen.de>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20240821125251.1571445-2-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/filter.c b/net/core/filter.c
index f3c72cf86099745ee8eb56f56711db92e6bfc84e..89f56fac48fbb1d51c910426d0332746832b8691 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -84,6 +84,7 @@
 #include <net/netkit.h>
 #include <linux/un.h>
 #include <net/xdp_sock_drv.h>
+#include <net/inet_dscp.h>
 
 #include "dev.h"
 
@@ -5899,7 +5900,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
                fl4.flowi4_iif = params->ifindex;
                fl4.flowi4_oif = 0;
        }
-       fl4.flowi4_tos = params->tos & IPTOS_RT_MASK;
+       fl4.flowi4_tos = params->tos & INET_DSCP_MASK;
        fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
        fl4.flowi4_flags = 0;