Currently, at xdp_adjust_tail_kern.c, MAX_PCKT_SIZE is limited
to 600. To make this size flexible, a new map 'pcktsz' is added.
By updating new packet size to this map from the userland,
xdp_adjust_tail_kern.o will use this value as a new max_pckt_size.
If no '-P <MAX_PCKT_SIZE>' option is used, the size of maximum packet
will be 600 as a default.
Signed-off-by: Daniel T. Lee <danieltimlee@xxxxxxxxx>
---
Changes in v2:
- Change the helper to fetch map from 'bpf_map__next' to
'bpf_object__find_map_fd_by_name'.
samples/bpf/xdp_adjust_tail_kern.c | 23 +++++++++++++++++++----
samples/bpf/xdp_adjust_tail_user.c | 28 ++++++++++++++++++++++------
2 files changed, 41 insertions(+), 10 deletions(-)
diff --git a/samples/bpf/xdp_adjust_tail_kern.c b/samples/bpf/xdp_adjust_tail_kern.c
index 411fdb21f8bc..d6d84ffe6a7a 100644
--- a/samples/bpf/xdp_adjust_tail_kern.c
+++ b/samples/bpf/xdp_adjust_tail_kern.c
@@ -25,6 +25,13 @@
#define ICMP_TOOBIG_SIZE 98
#define ICMP_TOOBIG_PAYLOAD_SIZE 92
+struct bpf_map_def SEC("maps") pcktsz = {
+ .type = BPF_MAP_TYPE_ARRAY,
+ .key_size = sizeof(__u32),
+ .value_size = sizeof(__u32),
+ .max_entries = 1,
+};
+
struct bpf_map_def SEC("maps") icmpcnt = {
.type = BPF_MAP_TYPE_ARRAY,
.key_size = sizeof(__u32),
@@ -64,7 +71,8 @@ static __always_inline void ipv4_csum(void *data_start, int data_size,
*csum = csum_fold_helper(*csum);
}
-static __always_inline int send_icmp4_too_big(struct xdp_md *xdp)
+static __always_inline int send_icmp4_too_big(struct xdp_md *xdp,
+ __u32 max_pckt_size)
{
int headroom = (int)sizeof(struct iphdr) + (int)sizeof(struct icmphdr);
@@ -92,7 +100,7 @@ static __always_inline int send_icmp4_too_big(struct xdp_md *xdp)
orig_iph = data + off;
icmp_hdr->type = ICMP_DEST_UNREACH;
icmp_hdr->code = ICMP_FRAG_NEEDED;
- icmp_hdr->un.frag.mtu = htons(MAX_PCKT_SIZE-sizeof(struct ethhdr));
+ icmp_hdr->un.frag.mtu = htons(max_pckt_size - sizeof(struct ethhdr));
icmp_hdr->checksum = 0;
ipv4_csum(icmp_hdr, ICMP_TOOBIG_PAYLOAD_SIZE, &csum);
icmp_hdr->checksum = csum;
@@ -118,14 +126,21 @@ static __always_inline int handle_ipv4(struct xdp_md *xdp)
{
void *data_end = (void *)(long)xdp->data_end;
void *data = (void *)(long)xdp->data;
+ __u32 max_pckt_size = MAX_PCKT_SIZE;
+ __u32 *pckt_sz;
+ __u32 key = 0;
int pckt_size = data_end - data;
int offset;
- if (pckt_size > MAX_PCKT_SIZE) {
+ pckt_sz = bpf_map_lookup_elem(&pcktsz, &key);
+ if (pckt_sz && *pckt_sz)
+ max_pckt_size = *pckt_sz;
+
+ if (pckt_size > max_pckt_size) {
offset = pckt_size - ICMP_TOOBIG_SIZE;
if (bpf_xdp_adjust_tail(xdp, 0 - offset))
return XDP_PASS;
- return send_icmp4_too_big(xdp);
+ return send_icmp4_too_big(xdp, max_pckt_size);
}
return XDP_PASS;
}
diff --git a/samples/bpf/xdp_adjust_tail_user.c b/samples/bpf/xdp_adjust_tail_user.c
index a3596b617c4c..aef6c69a48a7 100644
--- a/samples/bpf/xdp_adjust_tail_user.c
+++ b/samples/bpf/xdp_adjust_tail_user.c
@@ -23,6 +23,7 @@
#include "libbpf.h"
#define STATS_INTERVAL_S 2U
+#define MAX_PCKT_SIZE 600
static int ifindex = -1;
static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
@@ -72,6 +73,7 @@ static void usage(const char *cmd)
printf("Usage: %s [...]\n", cmd);
printf(" -i <ifname|ifindex> Interface\n");
printf(" -T <stop-after-X-seconds> Default: 0 (forever)\n");
+ printf(" -P <MAX_PCKT_SIZE> Default: %u\n", MAX_PCKT_SIZE);
printf(" -S use skb-mode\n");
printf(" -N enforce native mode\n");
printf(" -F force loading prog\n");
@@ -85,13 +87,14 @@ int main(int argc, char **argv)
.prog_type = BPF_PROG_TYPE_XDP,
};
unsigned char opt_flags[256] = {};
- const char *optstr = "i:T:SNFh";
+ const char *optstr = "i:T:P:SNFh";
struct bpf_prog_info info = {};
__u32 info_len = sizeof(info);
+ __u32 max_pckt_size = 0;
+ __u32 key = 0;
unsigned int kill_after_s = 0;
int i, prog_fd, map_fd, opt;
struct bpf_object *obj;
- struct bpf_map *map;
char filename[256];
int err;
@@ -110,6 +113,9 @@ int main(int argc, char **argv)
case 'T':
kill_after_s = atoi(optarg);
break;
+ case 'P':
+ max_pckt_size = atoi(optarg);
+ break;
case 'S':
xdp_flags |= XDP_FLAGS_SKB_MODE;
break;
@@ -150,12 +156,22 @@ int main(int argc, char **argv)
if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
return 1;
- map = bpf_map__next(NULL, obj);
- if (!map) {
- printf("finding a map in obj file failed\n");
+ /* update pcktsz map */
+ if (max_pckt_size) {
+ map_fd = bpf_object__find_map_fd_by_name(obj, "pcktsz");
+ if (!map_fd) {
+ printf("finding a pcktsz map in obj file failed\n");
+ return 1;
+ }
+ bpf_map_update_elem(map_fd, &key, &max_pckt_size, BPF_ANY);
+ }
+
+ /* fetch icmpcnt map */
+ map_fd = bpf_object__find_map_fd_by_name(obj, "icmpcnt");
+ if (!map_fd) {
+ printf("finding a icmpcnt map in obj file failed\n");
return 1;
}
- map_fd = bpf_map__fd(map);
if (!prog_fd) {
printf("load_bpf_file: %s\n", strerror(errno));
--
2.20.1
