mirror/xdp-project-bpf-examples
1
0
Fork 0
mirror of https://github.com/xdp-project/bpf-examples.git synced 2024-05-06 15:54:53 +00:00
Code Issues Projects Releases Wiki Activity

MTU-tests: Add tc_bpf program that increase packet size

Browse Source 
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
This commit is contained in:
Jesper Dangaard Brouer
2020-10-13 15:07:39 +02:00
parent 74bde6b32c
commit 00eaf20fae
2 changed files with 71 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
MTU-tests/Makefile
View File

@@ -1,8 +1,8 @@
# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
USER_TARGETS :=
BPF_TARGETS := tc_bpf_encap
EXTRA_DEPS := encap.h
BPF_TARGETS := tc_bpf_inc_pkt_size
# EXTRA_DEPS := encap.h
LIB_DIR = ../lib

69
MTU-tests/tc_bpf_inc_pkt_size.c Normal file
View File

@@ -0,0 +1,69 @@
#include <linux/bpf.h>
#include <linux/in6.h>
#include <bpf/bpf_helpers.h>
#include <xdp/parsing_helpers.h>
/* MTU is defined as L3 size (usually 1500 for Ethernet),
* but remember TC (and XDP) operate at L2.
*/
//#define PKT_SIZE_L3 1500
#define PKT_SIZE_L3 1501
//#define PKT_SIZE_L3 1505
//#define PKT_SIZE_L3 1600
//#define PKT_SIZE_L3 20000
//#define PKT_SIZE_L3 65535
#define OFFSET sizeof(struct iphdr)
#define ENCAP_TYPE BPF_F_ADJ_ROOM_ENCAP_L3_IPV4
SEC("classifier") int tc_inc_pkt_sz(struct __sk_buff *skb)
{
volatile void *data, *data_end;
int ret = BPF_DROP;
struct ethhdr *eth;
struct iphdr *iph;
int extra_len;
int len;
/* Desired packet size at L2 */
int pkt_size_l2 = PKT_SIZE_L3 + sizeof(*eth) ;
data = (void *)(long)skb->data;
data_end = (void *)(long)skb->data_end;
eth = (struct ethhdr *)data;
if (data + sizeof(*eth) > data_end)
return BPF_DROP;
/* Keep ARP resolution working */
if (eth->h_proto == bpf_htons(ETH_P_ARP)) {
ret = BPF_OK;
goto out;
}
len = (data_end - data);
extra_len = pkt_size_l2 - len;
if (bpf_skb_adjust_room(skb, extra_len, BPF_ADJ_ROOM_MAC, ENCAP_TYPE))
goto out;
// TODO: Handle if bpf_skb_adjust_room() cannot increase size,
// as it's only my patched kernel that drop the MTU check
/* Most re-load after bpf_skb_adjust_room() */
data = (void *)(long)skb->data;
data_end = (void *)(long)skb->data_end;
eth = (void *)data;
iph = (void *)(eth +1);
if (iph +1 > data_end)
goto out;
eth->h_proto = bpf_htons(ETH_P_IP);
ret = BPF_OK;
out:
return ret;
}
char _license[] SEC("license") = "GPL";