On Mon, 26 Aug 2019 18:57:22 +0900
"Daniel T. Lee" <danieltim...@gmail.com> wrote:
> 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 <danieltim...@gmail.com>
> ---
> samples/bpf/xdp_adjust_tail_kern.c | 23 +++++++++++++++++++----
> samples/bpf/xdp_adjust_tail_user.c | 21 +++++++++++++++++++--
> 2 files changed, 38 insertions(+), 6 deletions(-)
>
> diff --git a/samples/bpf/xdp_adjust_tail_kern.c
> b/samples/bpf/xdp_adjust_tail_kern.c
> index 411fdb21f8bc..4d53af370b68 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..dd3befa5e1fe 100644
> --- a/samples/bpf/xdp_adjust_tail_user.c
> +++ b/samples/bpf/xdp_adjust_tail_user.c
> @@ -72,6 +72,7 @@ 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: 600\n");
> printf(" -S use skb-mode\n");
> printf(" -N enforce native mode\n");
> printf(" -F force loading prog\n");
> @@ -85,9 +86,11 @@ 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;
> @@ -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;
> @@ -150,9 +156,20 @@ int main(int argc, char **argv)
> if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
> return 1;
>
> + /* update pcktsz map */
> map = bpf_map__next(NULL, obj);
> if (!map) {
> - printf("finding a map in obj file failed\n");
> + printf("finding a pcktsz map in obj file failed\n");
> + return 1;
> + }
> + map_fd = bpf_map__fd(map);
Consider using bpf_object__find_map_fd_by_name() here.
> + if (max_pckt_size)
> + bpf_map_update_elem(map_fd, &key, &max_pckt_size, BPF_ANY);
> +
> + /* fetch icmpcnt map */
> + map = bpf_map__next(map, obj);
> + if (!map) {
> + printf("finding a icmpcnt map in obj file failed\n");
> return 1;
> }
> map_fd = bpf_map__fd(map);
