From e3ecf048579afd7a673700d04893671627e85d57 Mon Sep 17 00:00:00 2001 From: Quentin Deslandes Date: Wed, 21 Feb 2024 16:16:20 +0100 Subject: [PATCH] ss: pretty-print BPF socket-local storage ss is able to print the map ID(s) for which a given socket has BPF socket-local storage defined (using --bpf-maps or --bpf-map-id=). However, the actual content of the map remains hidden. This change aims to pretty-print the socket-local storage content following the socket details, similar to what `bpftool map dump` would do. The exact output format is inspired by drgn, while the BTF data processing is similar to bpftool's. ss will use libbpf's btf_dump__dump_type_data() to ease pretty-printing of binary data. This requires out_bpf_sk_storage_print_fn() as a print callback function used by btf_dump__dump_type_data(). vout() is also introduced, which is similar to out() but accepts a va_list as parameter. ss' output remains unchanged unless --bpf-maps or --bpf-map-id= is used, in which case each socket containing BPF local storage will be followed by the content of the storage before the next socket's info is displayed. Signed-off-by: Quentin Deslandes Acked-by: Martin KaFai Lau Signed-off-by: David Ahern --- misc/ss.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 137 insertions(+), 11 deletions(-) diff --git a/misc/ss.c b/misc/ss.c index 2c7e7c58..3ebac132 100644 --- a/misc/ss.c +++ b/misc/ss.c @@ -61,7 +61,9 @@ #define ENABLE_BPF_SKSTORAGE_SUPPORT #include +#include #include +#include #if (LIBBPF_MAJOR_VERSION == 0) && (LIBBPF_MINOR_VERSION < 5) #warning "libbpf version 0.5 or later is required, disabling BPF socket-local storage support" @@ -1053,11 +1055,10 @@ static int buf_update(int len) } /* Append content to buffer as part of the current field */ -__attribute__((format(printf, 1, 2))) -static void out(const char *fmt, ...) +static void vout(const char *fmt, va_list args) { struct column *f = current_field; - va_list args; + va_list _args; char *pos; int len; @@ -1068,18 +1069,27 @@ static void out(const char *fmt, ...) buffer.head = buf_chunk_new(); again: /* Append to buffer: if we have a new chunk, print again */ + va_copy(_args, args); pos = buffer.cur->data + buffer.cur->len; - va_start(args, fmt); /* Limit to tail room. If we hit the limit, buf_update() will tell us */ - len = vsnprintf(pos, buf_chunk_avail(buffer.tail), fmt, args); - va_end(args); + len = vsnprintf(pos, buf_chunk_avail(buffer.tail), fmt, _args); if (buf_update(len)) goto again; } +__attribute__((format(printf, 1, 2))) +static void out(const char *fmt, ...) +{ + va_list args; + + va_start(args, fmt); + vout(fmt, args); + va_end(args); +} + static int print_left_spacing(struct column *f, int stored, int printed) { int s; @@ -3413,6 +3423,9 @@ static struct bpf_map_opts { struct bpf_sk_storage_map_info { unsigned int id; int fd; + struct bpf_map_info info; + struct btf *btf; + struct btf_dump *dump; } maps[MAX_NR_BPF_MAP_ID_OPTS]; bool show_all; } bpf_map_opts; @@ -3423,10 +3436,36 @@ static void bpf_map_opts_mixed_error(void) "ss: --bpf-maps and --bpf-map-id cannot be used together\n"); } +static int bpf_maps_opts_load_btf(struct bpf_map_info *info, struct btf **btf) +{ + if (info->btf_value_type_id) { + *btf = btf__load_from_kernel_by_id(info->btf_id); + if (!*btf) { + fprintf(stderr, "ss: failed to load BTF for map ID %u\n", + info->id); + return -1; + } + } else { + *btf = NULL; + } + + return 0; +} + +static void out_bpf_sk_storage_print_fn(void *ctx, const char *fmt, va_list args) +{ + vout(fmt, args); +} + static int bpf_map_opts_load_info(unsigned int map_id) { + struct btf_dump_opts dopts = { + .sz = sizeof(struct btf_dump_opts) + }; struct bpf_map_info info = {}; uint32_t len = sizeof(info); + struct btf_dump *dump; + struct btf *btf; int fd; int r; @@ -3464,8 +3503,25 @@ static int bpf_map_opts_load_info(unsigned int map_id) return -1; } + r = bpf_maps_opts_load_btf(&info, &btf); + if (r) { + close(fd); + return -1; + } + + dump = btf_dump__new(btf, out_bpf_sk_storage_print_fn, NULL, &dopts); + if (!dump) { + btf__free(btf); + close(fd); + fprintf(stderr, "Failed to create btf_dump object\n"); + return -1; + } + bpf_map_opts.maps[bpf_map_opts.nr_maps].id = map_id; - bpf_map_opts.maps[bpf_map_opts.nr_maps++].fd = fd; + bpf_map_opts.maps[bpf_map_opts.nr_maps].fd = fd; + bpf_map_opts.maps[bpf_map_opts.nr_maps].info = info; + bpf_map_opts.maps[bpf_map_opts.nr_maps].btf = btf; + bpf_map_opts.maps[bpf_map_opts.nr_maps++].dump = dump; return 0; } @@ -3517,8 +3573,11 @@ static void bpf_map_opts_destroy(void) { int i; - for (i = 0; i < bpf_map_opts.nr_maps; ++i) + for (i = 0; i < bpf_map_opts.nr_maps; ++i) { + btf_dump__free(bpf_map_opts.maps[i].dump); + btf__free(bpf_map_opts.maps[i].btf); close(bpf_map_opts.maps[i].fd); + } } static struct rtattr *bpf_map_opts_alloc_rta(void) @@ -3571,10 +3630,74 @@ static struct rtattr *bpf_map_opts_alloc_rta(void) return stgs_rta; } +static void out_bpf_sk_storage_oneline(struct bpf_sk_storage_map_info *info, + const void *data, size_t len) +{ + struct btf_dump_type_data_opts opts = { + .sz = sizeof(struct btf_dump_type_data_opts), + .emit_zeroes = 1, + .compact = 1 + }; + int r; + + out(" map_id:%d", info->id); + r = btf_dump__dump_type_data(info->dump, info->info.btf_value_type_id, + data, len, &opts); + if (r < 0) + out("failed to dump data: %d", r); +} + +static void out_bpf_sk_storage_multiline(struct bpf_sk_storage_map_info *info, + const void *data, size_t len) +{ + struct btf_dump_type_data_opts opts = { + .sz = sizeof(struct btf_dump_type_data_opts), + .indent_level = 2, + .emit_zeroes = 1 + }; + int r; + + out("\n\tmap_id:%d [\n", info->id); + + r = btf_dump__dump_type_data(info->dump, info->info.btf_value_type_id, + data, len, &opts); + if (r < 0) + out("\t\tfailed to dump data: %d", r); + + out("\n\t]"); +} + +static void out_bpf_sk_storage(int map_id, const void *data, size_t len) +{ + struct bpf_sk_storage_map_info *map_info; + + map_info = bpf_map_opts_get_info(map_id); + if (!map_info) { + /* The kernel might return a map we can't get info for, skip + * it but print the other ones. + */ + out("\n\tmap_id: %d failed to fetch info, skipping\n", map_id); + return; + } + + if (map_info->info.value_size != len) { + fprintf(stderr, + "map_id: %d: invalid value size, expecting %u, got %lu\n", + map_id, map_info->info.value_size, len); + return; + } + + if (oneline) + out_bpf_sk_storage_oneline(map_info, data, len); + else + out_bpf_sk_storage_multiline(map_info, data, len); +} + static void show_sk_bpf_storages(struct rtattr *bpf_stgs) { struct rtattr *tb[SK_DIAG_BPF_STORAGE_MAX + 1], *bpf_stg; - unsigned int rem; + unsigned int rem, map_id; + struct rtattr *value; for (bpf_stg = RTA_DATA(bpf_stgs), rem = RTA_PAYLOAD(bpf_stgs); RTA_OK(bpf_stg, rem); bpf_stg = RTA_NEXT(bpf_stg, rem)) { @@ -3586,8 +3709,11 @@ static void show_sk_bpf_storages(struct rtattr *bpf_stgs) (struct rtattr *)bpf_stg); if (tb[SK_DIAG_BPF_STORAGE_MAP_ID]) { - out(" map_id:%u", - rta_getattr_u32(tb[SK_DIAG_BPF_STORAGE_MAP_ID])); + map_id = rta_getattr_u32(tb[SK_DIAG_BPF_STORAGE_MAP_ID]); + value = tb[SK_DIAG_BPF_STORAGE_MAP_VALUE]; + + out_bpf_sk_storage(map_id, RTA_DATA(value), + RTA_PAYLOAD(value)); } } } -- 2.41.0