From 8fdf5b780a148c4a7490c211acad3c01b4dde6ac Mon Sep 17 00:00:00 2001 From: "Daniel T. Lee" Date: Tue, 8 Oct 2019 02:21:17 +0900 Subject: 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 ' 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 Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20191007172117.3916-1-danieltimlee@gmail.com --- samples/bpf/xdp_adjust_tail_kern.c | 7 +++++-- samples/bpf/xdp_adjust_tail_user.c | 29 ++++++++++++++++++++--------- 2 files changed, 25 insertions(+), 11 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; diff --git a/samples/bpf/xdp_adjust_tail_user.c b/samples/bpf/xdp_adjust_tail_user.c index a3596b617c4c..d86e9ad0356b 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 Interface\n"); printf(" -T Default: 0 (forever)\n"); + printf(" -P 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); unsigned int kill_after_s = 0; int i, prog_fd, map_fd, opt; struct bpf_object *obj; - struct bpf_map *map; + __u32 max_pckt_size = 0; + __u32 key = 0; 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; @@ -150,15 +156,20 @@ 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"); - return 1; + /* static global var 'max_pcktsz' is accessible from .data section */ + if (max_pckt_size) { + map_fd = bpf_object__find_map_fd_by_name(obj, "xdp_adju.data"); + if (map_fd < 0) { + printf("finding a max_pcktsz map in obj file failed\n"); + return 1; + } + bpf_map_update_elem(map_fd, &key, &max_pckt_size, BPF_ANY); } - map_fd = bpf_map__fd(map); - if (!prog_fd) { - printf("load_bpf_file: %s\n", strerror(errno)); + /* fetch icmpcnt map */ + map_fd = bpf_object__find_map_fd_by_name(obj, "icmpcnt"); + if (map_fd < 0) { + printf("finding a icmpcnt map in obj file failed\n"); return 1; } -- cgit v1.2.3