From 8740ca9dcd3ccf1c75c362900cb3218ae3204cf5 Mon Sep 17 00:00:00 2001 From: Quentin Deslandes Date: Wed, 21 Feb 2024 16:16:19 +0100 Subject: [PATCH] ss: add support for BPF socket-local storage While sock_diag is able to return BPF socket-local storage in response to INET_DIAG_REQ_SK_BPF_STORAGES requests, ss doesn't request it. This change introduces the --bpf-maps and --bpf-map-id= options to request BPF socket-local storage for all SK_STORAGE maps, or only specific ones. The bigger part of this change will check the requested map IDs and ensure they are valid. The column COL_EXT is used to print the socket-local data into. When --bpf-maps is used, ss will send an empty INET_DIAG_REQ_SK_BPF_STORAGES request, in return the kernel will send all the BPF socket-local storage entries for a given socket. The BTF data for each map is loaded on demand, as ss can't predict which map ID are used. When --bpf-map-id=ID is used, a file descriptor to the requested maps is open to 1) ensure the map doesn't disappear before the data is printed, and 2) ensure the map type is BPF_MAP_TYPE_SK_STORAGE. The BTF data for each requested map is loaded before the request is sent to the kernel. Co-developed-by: Martin KaFai Lau Signed-off-by: Martin KaFai Lau Signed-off-by: Quentin Deslandes Signed-off-by: David Ahern --- misc/ss.c | 272 +++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 269 insertions(+), 3 deletions(-) diff --git a/misc/ss.c b/misc/ss.c index 72a841be..2c7e7c58 100644 --- a/misc/ss.c +++ b/misc/ss.c @@ -51,6 +51,24 @@ #include #include +#ifdef HAVE_LIBBPF +/* If libbpf is new enough (0.5+), support for pretty-printing BPF socket-local + * storage is enabled, otherwise we emit a warning and disable it. + * ENABLE_BPF_SKSTORAGE_SUPPORT is only used to gate the socket-local storage + * feature, so this wouldn't prevent any feature relying on HAVE_LIBBPF to be + * usable. + */ +#define ENABLE_BPF_SKSTORAGE_SUPPORT + +#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" +#undef ENABLE_BPF_SKSTORAGE_SUPPORT +#endif +#endif + #if HAVE_RPC #include #include @@ -3384,6 +3402,202 @@ static void parse_diag_msg(struct nlmsghdr *nlh, struct sockstat *s) memcpy(s->remote.data, r->id.idiag_dst, s->local.bytelen); } +#ifdef ENABLE_BPF_SKSTORAGE_SUPPORT + +#define MAX_NR_BPF_MAP_ID_OPTS 32 + +struct btf; + +static struct bpf_map_opts { + unsigned int nr_maps; + struct bpf_sk_storage_map_info { + unsigned int id; + int fd; + } maps[MAX_NR_BPF_MAP_ID_OPTS]; + bool show_all; +} bpf_map_opts; + +static void bpf_map_opts_mixed_error(void) +{ + fprintf(stderr, + "ss: --bpf-maps and --bpf-map-id cannot be used together\n"); +} + +static int bpf_map_opts_load_info(unsigned int map_id) +{ + struct bpf_map_info info = {}; + uint32_t len = sizeof(info); + int fd; + int r; + + if (bpf_map_opts.nr_maps == MAX_NR_BPF_MAP_ID_OPTS) { + fprintf(stderr, + "ss: too many (> %u) BPF socket-local storage maps found, skipping map ID %u\n", + MAX_NR_BPF_MAP_ID_OPTS, map_id); + return 0; + } + + fd = bpf_map_get_fd_by_id(map_id); + if (fd < 0) { + if (errno == -ENOENT) + return 0; + + fprintf(stderr, "ss: cannot get fd for BPF map ID %u%s\n", + map_id, errno == EPERM ? + ": missing root permissions, CAP_BPF, or CAP_SYS_ADMIN" : ""); + return -1; + } + + r = bpf_obj_get_info_by_fd(fd, &info, &len); + if (r) { + fprintf(stderr, "ss: failed to get info for BPF map ID %u\n", + map_id); + close(fd); + return -1; + } + + if (info.type != BPF_MAP_TYPE_SK_STORAGE) { + fprintf(stderr, + "ss: BPF map with ID %s has type ID %d, expecting %d ('sk_storage')\n", + optarg, info.type, BPF_MAP_TYPE_SK_STORAGE); + close(fd); + 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; + + return 0; +} + +static struct bpf_sk_storage_map_info *bpf_map_opts_get_info( + unsigned int map_id) +{ + unsigned int i; + int r; + + for (i = 0; i < bpf_map_opts.nr_maps; ++i) { + if (bpf_map_opts.maps[i].id == map_id) + return &bpf_map_opts.maps[i]; + } + + r = bpf_map_opts_load_info(map_id); + if (r) + return NULL; + + return &bpf_map_opts.maps[bpf_map_opts.nr_maps - 1]; +} + +static int bpf_map_opts_add_id(const char *optarg) +{ + size_t optarg_len; + unsigned long id; + char *end; + + if (bpf_map_opts.show_all) { + bpf_map_opts_mixed_error(); + return -1; + } + + optarg_len = strlen(optarg); + id = strtoul(optarg, &end, 0); + if (end != optarg + optarg_len || id == 0 || id >= UINT32_MAX) { + fprintf(stderr, "ss: invalid BPF map ID %s\n", optarg); + return -1; + } + + /* Force lazy loading of the map's data. */ + if (!bpf_map_opts_get_info(id)) + return -1; + + return 0; +} + +static void bpf_map_opts_destroy(void) +{ + int i; + + for (i = 0; i < bpf_map_opts.nr_maps; ++i) + close(bpf_map_opts.maps[i].fd); +} + +static struct rtattr *bpf_map_opts_alloc_rta(void) +{ + struct rtattr *stgs_rta, *fd_rta; + size_t total_size; + unsigned int i; + void *buf; + + /* If bpf_map_opts.show_all == true, we will send an empty message to + * the kernel, which will return all the socket-local data attached to + * a socket, no matter their map ID + */ + if (bpf_map_opts.show_all) { + total_size = RTA_LENGTH(0); + } else { + total_size = RTA_LENGTH(RTA_LENGTH(sizeof(int)) * + bpf_map_opts.nr_maps); + } + + buf = malloc(total_size); + if (!buf) + return NULL; + + stgs_rta = buf; + stgs_rta->rta_type = INET_DIAG_REQ_SK_BPF_STORAGES | NLA_F_NESTED; + stgs_rta->rta_len = total_size; + + /* If inet_show_netlink() retries fetching socket data, nr_maps might + * be different from 0, even with show_all == true, so we return early + * to avoid inserting specific map IDs into the request. + */ + if (bpf_map_opts.show_all) + return stgs_rta; + + buf = RTA_DATA(stgs_rta); + for (i = 0; i < bpf_map_opts.nr_maps; i++) { + int *fd; + + fd_rta = buf; + fd_rta->rta_type = SK_DIAG_BPF_STORAGE_REQ_MAP_FD; + fd_rta->rta_len = RTA_LENGTH(sizeof(int)); + + fd = RTA_DATA(fd_rta); + *fd = bpf_map_opts.maps[i].fd; + + buf += fd_rta->rta_len; + } + + return stgs_rta; +} + +static void show_sk_bpf_storages(struct rtattr *bpf_stgs) +{ + struct rtattr *tb[SK_DIAG_BPF_STORAGE_MAX + 1], *bpf_stg; + unsigned int rem; + + for (bpf_stg = RTA_DATA(bpf_stgs), rem = RTA_PAYLOAD(bpf_stgs); + RTA_OK(bpf_stg, rem); bpf_stg = RTA_NEXT(bpf_stg, rem)) { + + if ((bpf_stg->rta_type & NLA_TYPE_MASK) != SK_DIAG_BPF_STORAGE) + continue; + + parse_rtattr_nested(tb, SK_DIAG_BPF_STORAGE_MAX, + (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])); + } + } +} + +static bool bpf_map_opts_is_enabled(void) +{ + return bpf_map_opts.nr_maps || bpf_map_opts.show_all; +} +#endif + static int inet_show_sock(struct nlmsghdr *nlh, struct sockstat *s) { @@ -3391,8 +3605,9 @@ static int inet_show_sock(struct nlmsghdr *nlh, struct inet_diag_msg *r = NLMSG_DATA(nlh); unsigned char v6only = 0; - parse_rtattr(tb, INET_DIAG_MAX, (struct rtattr *)(r+1), - nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*r))); + parse_rtattr_flags(tb, INET_DIAG_MAX, (struct rtattr *)(r+1), + nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*r)), + NLA_F_NESTED); if (tb[INET_DIAG_PROTOCOL]) s->type = rta_getattr_u8(tb[INET_DIAG_PROTOCOL]); @@ -3489,6 +3704,11 @@ static int inet_show_sock(struct nlmsghdr *nlh, } sctp_ino = s->ino; +#ifdef ENABLE_BPF_SKSTORAGE_SUPPORT + if (tb[INET_DIAG_SK_BPF_STORAGES]) + show_sk_bpf_storages(tb[INET_DIAG_SK_BPF_STORAGES]); +#endif + return 0; } @@ -3570,13 +3790,14 @@ static int sockdiag_send(int family, int fd, int protocol, struct filter *f) { struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK }; DIAG_REQUEST(req, struct inet_diag_req_v2 r); + struct rtattr *bpf_rta = NULL; char *bc = NULL; int bclen; __u32 proto; struct msghdr msg; struct rtattr rta_bc; struct rtattr rta_proto; - struct iovec iov[5]; + struct iovec iov[6]; int iovlen = 1; if (family == PF_UNSPEC) @@ -3629,6 +3850,20 @@ static int sockdiag_send(int family, int fd, int protocol, struct filter *f) iovlen += 2; } +#ifdef ENABLE_BPF_SKSTORAGE_SUPPORT + if (bpf_map_opts_is_enabled()) { + bpf_rta = bpf_map_opts_alloc_rta(); + if (!bpf_rta) { + fprintf(stderr, + "ss: cannot alloc request for --bpf-map\n"); + return -1; + } + + iov[iovlen++] = (struct iovec){ bpf_rta, bpf_rta->rta_len }; + req.nlh.nlmsg_len += bpf_rta->rta_len; + } +#endif + msg = (struct msghdr) { .msg_name = (void *)&nladdr, .msg_namelen = sizeof(nladdr), @@ -3637,10 +3872,13 @@ static int sockdiag_send(int family, int fd, int protocol, struct filter *f) }; if (sendmsg(fd, &msg, 0) < 0) { + free(bpf_rta); close(fd); return -1; } + free(bpf_rta); + return 0; } @@ -5361,6 +5599,10 @@ static void _usage(FILE *dest) " --tos show tos and priority information\n" " --cgroup show cgroup information\n" " -b, --bpf show bpf filter socket information\n" +#ifdef ENABLE_BPF_SKSTORAGE_SUPPORT +" --bpf-maps show all BPF socket-local storage maps\n" +" --bpf-map-id=MAP-ID show a BPF socket-local storage map\n" +#endif " -E, --events continually display sockets as they are destroyed\n" " -Z, --context display task SELinux security contexts\n" " -z, --contexts display task and socket SELinux security contexts\n" @@ -5487,6 +5729,9 @@ wrong_state: #define OPT_INET_SOCKOPT 262 +#define OPT_BPF_MAPS 263 +#define OPT_BPF_MAP_ID 264 + static const struct option long_opts[] = { { "numeric", 0, 0, 'n' }, { "resolve", 0, 0, 'r' }, @@ -5533,6 +5778,10 @@ static const struct option long_opts[] = { { "mptcp", 0, 0, 'M' }, { "oneline", 0, 0, 'O' }, { "inet-sockopt", 0, 0, OPT_INET_SOCKOPT }, +#ifdef ENABLE_BPF_SKSTORAGE_SUPPORT + { "bpf-maps", 0, 0, OPT_BPF_MAPS}, + { "bpf-map-id", 1, 0, OPT_BPF_MAP_ID}, +#endif { 0 } }; @@ -5741,6 +5990,19 @@ int main(int argc, char *argv[]) case OPT_INET_SOCKOPT: show_inet_sockopt = 1; break; +#ifdef ENABLE_BPF_SKSTORAGE_SUPPORT + case OPT_BPF_MAPS: + if (bpf_map_opts.nr_maps) { + bpf_map_opts_mixed_error(); + return -1; + } + bpf_map_opts.show_all = true; + break; + case OPT_BPF_MAP_ID: + if (bpf_map_opts_add_id(optarg)) + exit(1); + break; +#endif case 'h': help(); case '?': @@ -5880,6 +6142,10 @@ int main(int argc, char *argv[]) if (show_processes || show_threads || show_proc_ctx || show_sock_ctx) user_ent_destroy(); +#ifdef ENABLE_BPF_SKSTORAGE_SUPPORT + bpf_map_opts_destroy(); +#endif + render(); return 0; -- 2.41.0