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| author | Daniel T. Lee <danieltimlee@gmail.com> | 2019-10-08 02:21:17 +0900 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2019-10-07 20:22:27 -0700 |
| commit | 8fdf5b780a148c4a7490c211acad3c01b4dde6ac (patch) | |
| tree | a7e9a4d1bae271f7eaeafecf501f75355525e2d6 /samples/bpf/xdp_adjust_tail_kern.c | |
| parent | 72ccd9200f218a7eb2933a93e69a79a1ac984d83 (diff) | |
| download | lwn-8fdf5b780a148c4a7490c211acad3c01b4dde6ac.tar.gz lwn-8fdf5b780a148c4a7490c211acad3c01b4dde6ac.zip | |
samples: bpf: Add max_pckt_size option at xdp_adjust_tail
Currently, at xdp_adjust_tail_kern.c, MAX_PCKT_SIZE is limited
to 600. To make this size flexible, static global variable
'max_pcktsz' is added.
By updating new packet size from the user space, xdp_adjust_tail_kern.o
will use this value as a new max packet size.
This static global variable can be accesible from .data section with
bpf_object__find_map* from user space, since it is considered as
internal map (accessible with .bss/.data/.rodata suffix).
If no '-P <MAX_PCKT_SIZE>' option is used, the size of maximum packet
will be 600 as a default.
For clarity, change the helper to fetch map from 'bpf_map__next'
to 'bpf_object__find_map_fd_by_name'. Also, changed the way to
test prog_fd, map_fd from '!= 0' to '< 0', since fd could be 0
when stdin is closed.
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191007172117.3916-1-danieltimlee@gmail.com
Diffstat (limited to 'samples/bpf/xdp_adjust_tail_kern.c')
| -rw-r--r-- | samples/bpf/xdp_adjust_tail_kern.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/samples/bpf/xdp_adjust_tail_kern.c b/samples/bpf/xdp_adjust_tail_kern.c index 411fdb21f8bc..c616508befb9 100644 --- a/samples/bpf/xdp_adjust_tail_kern.c +++ b/samples/bpf/xdp_adjust_tail_kern.c @@ -25,6 +25,9 @@ #define ICMP_TOOBIG_SIZE 98 #define ICMP_TOOBIG_PAYLOAD_SIZE 92 +/* volatile to prevent compiler optimizations */ +static volatile __u32 max_pcktsz = MAX_PCKT_SIZE; + struct bpf_map_def SEC("maps") icmpcnt = { .type = BPF_MAP_TYPE_ARRAY, .key_size = sizeof(__u32), @@ -92,7 +95,7 @@ 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_pcktsz - sizeof(struct ethhdr)); icmp_hdr->checksum = 0; ipv4_csum(icmp_hdr, ICMP_TOOBIG_PAYLOAD_SIZE, &csum); icmp_hdr->checksum = csum; @@ -121,7 +124,7 @@ static __always_inline int handle_ipv4(struct xdp_md *xdp) int pckt_size = data_end - data; int offset; - if (pckt_size > MAX_PCKT_SIZE) { + if (pckt_size > max(max_pcktsz, ICMP_TOOBIG_SIZE)) { offset = pckt_size - ICMP_TOOBIG_SIZE; if (bpf_xdp_adjust_tail(xdp, 0 - offset)) return XDP_PASS; |