From e5e35e754c28724d5c619f2ec805fd221f8d59ce Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Mon, 8 Mar 2021 15:59:18 +0100 Subject: bpf: BPF-helper for MTU checking add length input The FIB lookup example[1] show how the IP-header field tot_len (iph->tot_len) is used as input to perform the MTU check. This patch extend the BPF-helper bpf_check_mtu() with the same ability to provide the length as user parameter input, via mtu_len parameter. This still needs to be done before the bpf_check_mtu() helper API becomes frozen. [1] samples/bpf/xdp_fwd_kern.c Fixes: 34b2021cc616 ("bpf: Add BPF-helper for MTU checking") Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Daniel Borkmann Acked-by: John Fastabend Link: https://lore.kernel.org/bpf/161521555850.3515614.6533850861569774444.stgit@firesoul --- include/uapi/linux/bpf.h | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) (limited to 'include/uapi') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 79c893310492..4ba4ef0ff63a 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3850,7 +3850,7 @@ union bpf_attr { * * long bpf_check_mtu(void *ctx, u32 ifindex, u32 *mtu_len, s32 len_diff, u64 flags) * Description - * Check ctx packet size against exceeding MTU of net device (based + * Check packet size against exceeding MTU of net device (based * on *ifindex*). This helper will likely be used in combination * with helpers that adjust/change the packet size. * @@ -3867,6 +3867,14 @@ union bpf_attr { * against the current net device. This is practical if this isn't * used prior to redirect. * + * On input *mtu_len* must be a valid pointer, else verifier will + * reject BPF program. If the value *mtu_len* is initialized to + * zero then the ctx packet size is use. When value *mtu_len* is + * provided as input this specify the L3 length that the MTU check + * is done against. Remember XDP and TC length operate at L2, but + * this value is L3 as this correlate to MTU and IP-header tot_len + * values which are L3 (similar behavior as bpf_fib_lookup). + * * The Linux kernel route table can configure MTUs on a more * specific per route level, which is not provided by this helper. * For route level MTU checks use the **bpf_fib_lookup**\ () @@ -3891,11 +3899,9 @@ union bpf_attr { * * On return *mtu_len* pointer contains the MTU value of the net * device. Remember the net device configured MTU is the L3 size, - * which is returned here and XDP and TX length operate at L2. + * which is returned here and XDP and TC length operate at L2. * Helper take this into account for you, but remember when using - * MTU value in your BPF-code. On input *mtu_len* must be a valid - * pointer and be initialized (to zero), else verifier will reject - * BPF program. + * MTU value in your BPF-code. * * Return * * 0 on success, and populate MTU value in *mtu_len* pointer. -- cgit v1.2.3 From e43accba9b071dcd106b5e7643b1b106a158cbb1 Mon Sep 17 00:00:00 2001 From: Ido Schimmel Date: Wed, 24 Mar 2021 21:43:32 +0200 Subject: psample: Fix user API breakage Cited commit added a new attribute before the existing group reference count attribute, thereby changing its value and breaking existing applications on new kernels. Before: # psample -l libpsample ERROR psample_group_foreach: failed to recv message: Operation not supported After: # psample -l Group Num Refcount Group Seq 1 1 0 Fix by restoring the value of the old attribute and remove the misleading comments from the enumerator to avoid future bugs. Cc: stable@vger.kernel.org Fixes: d8bed686ab96 ("net: psample: Add tunnel support") Signed-off-by: Ido Schimmel Reported-by: Adiel Bidani Reviewed-by: Jiri Pirko Reviewed-by: Petr Machata Signed-off-by: David S. Miller --- include/uapi/linux/psample.h | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) (limited to 'include/uapi') diff --git a/include/uapi/linux/psample.h b/include/uapi/linux/psample.h index aea26ab1431c..bff5032c98df 100644 --- a/include/uapi/linux/psample.h +++ b/include/uapi/linux/psample.h @@ -3,7 +3,6 @@ #define __UAPI_PSAMPLE_H enum { - /* sampled packet metadata */ PSAMPLE_ATTR_IIFINDEX, PSAMPLE_ATTR_OIFINDEX, PSAMPLE_ATTR_ORIGSIZE, @@ -11,10 +10,8 @@ enum { PSAMPLE_ATTR_GROUP_SEQ, PSAMPLE_ATTR_SAMPLE_RATE, PSAMPLE_ATTR_DATA, - PSAMPLE_ATTR_TUNNEL, - - /* commands attributes */ PSAMPLE_ATTR_GROUP_REFCOUNT, + PSAMPLE_ATTR_TUNNEL, __PSAMPLE_ATTR_MAX }; -- cgit v1.2.3