| Message ID | 20210326230938.49998-7-maciej.fijalkowski@intel.com |
|---|---|
| State | New |
| Headers | show |
| Series | AF_XDP selftests improvements & bpf_link | expand |
Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes: > Currently, if there are multiple xdpsock instances running on a single > interface and in case one of the instances is terminated, the rest of > them are left in an inoperable state due to the fact of unloaded XDP > prog from interface. > > Consider the scenario below: > > // load xdp prog and xskmap and add entry to xskmap at idx 10 > $ sudo ./xdpsock -i ens801f0 -t -q 10 > > // add entry to xskmap at idx 11 > $ sudo ./xdpsock -i ens801f0 -t -q 11 > > terminate one of the processes and another one is unable to work due to > the fact that the XDP prog was unloaded from interface. > > To address that, step away from setting bpf prog in favour of bpf_link. > This means that refcounting of BPF resources will be done automatically > by bpf_link itself. > > Provide backward compatibility by checking if underlying system is > bpf_link capable. Do this by looking up/creating bpf_link on loopback > device. If it failed in any way, stick with netlink-based XDP prog. > therwise, use bpf_link-based logic. > > When setting up BPF resources during xsk socket creation, check whether > bpf_link for a given ifindex already exists via set of calls to > bpf_link_get_next_id -> bpf_link_get_fd_by_id -> bpf_obj_get_info_by_fd > and comparing the ifindexes from bpf_link and xsk socket. > > For case where resources exist but they are not AF_XDP related, bail out > and ask user to remove existing prog and then retry. > > Lastly, do a bit of refactoring within __xsk_setup_xdp_prog and pull out > existing code branches based on prog_id value onto separate functions > that are responsible for resource initialization if prog_id was 0 and > for lookup existing resources for non-zero prog_id as that implies that > XDP program is present on the underlying net device. This in turn makes > it easier to follow, especially the teardown part of both branches. > > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> The logic is much improved in this version! A few smallish issues below: > --- > tools/lib/bpf/xsk.c | 259 ++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 214 insertions(+), 45 deletions(-) > > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c > index 526fc35c0b23..c75067f0035f 100644 > --- a/tools/lib/bpf/xsk.c > +++ b/tools/lib/bpf/xsk.c > @@ -28,6 +28,7 @@ > #include <sys/mman.h> > #include <sys/socket.h> > #include <sys/types.h> > +#include <linux/if_link.h> > > #include "bpf.h" > #include "libbpf.h" > @@ -70,8 +71,10 @@ struct xsk_ctx { > int ifindex; > struct list_head list; > int prog_fd; > + int link_fd; > int xsks_map_fd; > char ifname[IFNAMSIZ]; > + bool has_bpf_link; > }; > > struct xsk_socket { > @@ -409,7 +412,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) > static const int log_buf_size = 16 * 1024; > struct xsk_ctx *ctx = xsk->ctx; > char log_buf[log_buf_size]; > - int err, prog_fd; > + int prog_fd; > > /* This is the fallback C-program: > * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx) > @@ -499,14 +502,43 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) > return prog_fd; > } > > - err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, prog_fd, > - xsk->config.xdp_flags); > + ctx->prog_fd = prog_fd; > + return 0; > +} > + > +static int xsk_create_bpf_link(struct xsk_socket *xsk) > +{ > + /* bpf_link only accepts XDP_FLAGS_MODES, but xsk->config.xdp_flags > + * might have set XDP_FLAGS_UPDATE_IF_NOEXIST > + */ > + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, > + .flags = (xsk->config.xdp_flags & XDP_FLAGS_MODES)); This will silently suppress any new flags as well; that's not a good idea. Rather mask out the particular flag (UPDATE_IF_NOEXIST) and pass everything else through so the kernel can reject invalid ones. > + struct xsk_ctx *ctx = xsk->ctx; > + __u32 prog_id = 0; > + int link_fd; > + int err; > + > + err = bpf_get_link_xdp_id(ctx->ifindex, &prog_id, xsk->config.xdp_flags); > if (err) { > - close(prog_fd); > + pr_warn("getting XDP prog id failed\n"); > return err; > } > > - ctx->prog_fd = prog_fd; > + /* if there's a netlink-based XDP prog loaded on interface, bail out > + * and ask user to do the removal by himself > + */ > + if (prog_id) { > + pr_warn("Netlink-based XDP prog detected, please unload it in order to launch AF_XDP prog\n"); > + return -EINVAL; > + } > + > + link_fd = bpf_link_create(ctx->prog_fd, ctx->ifindex, BPF_XDP, &opts); > + if (link_fd < 0) { > + pr_warn("bpf_link_create failed: %s\n", strerror(errno)); > + return link_fd; > + } > + > + ctx->link_fd = link_fd; > return 0; > } > > @@ -625,7 +657,6 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk) > close(fd); > } > > - err = 0; > if (ctx->xsks_map_fd == -1) > err = -ENOENT; > > @@ -642,6 +673,97 @@ static int xsk_set_bpf_maps(struct xsk_socket *xsk) > &xsk->fd, 0); > } > > +static int xsk_link_lookup(int ifindex, __u32 *prog_id, int *link_fd) > +{ > + struct bpf_link_info link_info; > + __u32 link_len; > + __u32 id = 0; > + int err; > + int fd; > + > + while (true) { > + err = bpf_link_get_next_id(id, &id); > + if (err) { > + if (errno == ENOENT) { > + err = 0; > + break; > + } > + pr_warn("can't get next link: %s\n", strerror(errno)); > + break; > + } > + > + fd = bpf_link_get_fd_by_id(id); > + if (fd < 0) { > + if (errno == ENOENT) > + continue; > + pr_warn("can't get link by id (%u): %s\n", id, strerror(errno)); > + err = -errno; > + break; > + } > + > + link_len = sizeof(struct bpf_link_info); > + memset(&link_info, 0, link_len); > + err = bpf_obj_get_info_by_fd(fd, &link_info, &link_len); > + if (err) { > + pr_warn("can't get link info: %s\n", strerror(errno)); > + close(fd); > + break; > + } > + if (link_info.type == BPF_LINK_TYPE_XDP) { > + if (link_info.xdp.ifindex == ifindex) { > + *link_fd = fd; > + if (prog_id) > + *prog_id = link_info.prog_id; > + break; > + } > + } > + close(fd); > + } > + > + return err; > +} > + > +static bool xsk_probe_bpf_link(void) > +{ > + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, > + .flags = XDP_FLAGS_SKB_MODE); > + struct bpf_load_program_attr prog_attr; > + struct bpf_insn insns[2] = { > + BPF_MOV64_IMM(BPF_REG_0, XDP_PASS), > + BPF_EXIT_INSN() > + }; > + int prog_fd, link_fd = -1; > + int ifindex_lo = 1; > + bool ret = false; > + int err; > + > + err = xsk_link_lookup(ifindex_lo, NULL, &link_fd); > + if (err) > + return ret; > + > + if (link_fd >= 0) > + return true; > + > + memset(&prog_attr, 0, sizeof(prog_attr)); > + prog_attr.prog_type = BPF_PROG_TYPE_XDP; > + prog_attr.insns = insns; > + prog_attr.insns_cnt = ARRAY_SIZE(insns); > + prog_attr.license = "GPL"; > + > + prog_fd = bpf_load_program_xattr(&prog_attr, NULL, 0); > + if (prog_fd < 0) > + return ret; > + > + link_fd = bpf_link_create(prog_fd, ifindex_lo, BPF_XDP, &opts); > + if (link_fd >= 0) > + ret = true; > + > + close(prog_fd); > + close(link_fd); This potentially calls close() on an invalid link_fd... > + > + return ret; > +} > + > static int xsk_create_xsk_struct(int ifindex, struct xsk_socket *xsk) > { > char ifname[IFNAMSIZ]; > @@ -663,64 +785,108 @@ static int xsk_create_xsk_struct(int ifindex, struct xsk_socket *xsk) > ctx->ifname[IFNAMSIZ - 1] = 0; > > xsk->ctx = ctx; > + xsk->ctx->has_bpf_link = xsk_probe_bpf_link(); > > return 0; > } > > -static int __xsk_setup_xdp_prog(struct xsk_socket *_xdp, > - int *xsks_map_fd) > +static int xsk_init_xdp_res(struct xsk_socket *xsk, > + int *xsks_map_fd) > { > - struct xsk_socket *xsk = _xdp; > struct xsk_ctx *ctx = xsk->ctx; > - __u32 prog_id = 0; > int err; > > - err = bpf_get_link_xdp_id(ctx->ifindex, &prog_id, > - xsk->config.xdp_flags); > + err = xsk_create_bpf_maps(xsk); > if (err) > return err; > > - if (!prog_id) { > - err = xsk_create_bpf_maps(xsk); > - if (err) > - return err; > + err = xsk_load_xdp_prog(xsk); > + if (err) > + goto err_load_xdp_prog; > > - err = xsk_load_xdp_prog(xsk); > - if (err) { > - goto err_load_xdp_prog; > - } > - } else { > - ctx->prog_fd = bpf_prog_get_fd_by_id(prog_id); > - if (ctx->prog_fd < 0) > - return -errno; > - err = xsk_lookup_bpf_maps(xsk); > - if (err) { > - close(ctx->prog_fd); > - return err; > - } > - } > + if (ctx->has_bpf_link) > + err = xsk_create_bpf_link(xsk); > + else > + err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, ctx->prog_fd, > + xsk->config.xdp_flags); > > - if (xsk->rx) { > - err = xsk_set_bpf_maps(xsk); > - if (err) { > - if (!prog_id) { > - goto err_set_bpf_maps; > - } else { > - close(ctx->prog_fd); > - return err; > - } > - } > - } > - if (xsks_map_fd) > - *xsks_map_fd = ctx->xsks_map_fd; > + if (err) > + goto err_atach_xdp_prog; s/atach/attach/ -Toke
On Mon, Mar 29, 2021 at 01:05:44PM +0200, Toke Høiland-Jørgensen wrote: > Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes: > > > Currently, if there are multiple xdpsock instances running on a single > > interface and in case one of the instances is terminated, the rest of > > them are left in an inoperable state due to the fact of unloaded XDP > > prog from interface. > > > > Consider the scenario below: > > > > // load xdp prog and xskmap and add entry to xskmap at idx 10 > > $ sudo ./xdpsock -i ens801f0 -t -q 10 > > > > // add entry to xskmap at idx 11 > > $ sudo ./xdpsock -i ens801f0 -t -q 11 > > > > terminate one of the processes and another one is unable to work due to > > the fact that the XDP prog was unloaded from interface. > > > > To address that, step away from setting bpf prog in favour of bpf_link. > > This means that refcounting of BPF resources will be done automatically > > by bpf_link itself. > > > > Provide backward compatibility by checking if underlying system is > > bpf_link capable. Do this by looking up/creating bpf_link on loopback > > device. If it failed in any way, stick with netlink-based XDP prog. > > therwise, use bpf_link-based logic. > > > > When setting up BPF resources during xsk socket creation, check whether > > bpf_link for a given ifindex already exists via set of calls to > > bpf_link_get_next_id -> bpf_link_get_fd_by_id -> bpf_obj_get_info_by_fd > > and comparing the ifindexes from bpf_link and xsk socket. > > > > For case where resources exist but they are not AF_XDP related, bail out > > and ask user to remove existing prog and then retry. > > > > Lastly, do a bit of refactoring within __xsk_setup_xdp_prog and pull out > > existing code branches based on prog_id value onto separate functions > > that are responsible for resource initialization if prog_id was 0 and > > for lookup existing resources for non-zero prog_id as that implies that > > XDP program is present on the underlying net device. This in turn makes > > it easier to follow, especially the teardown part of both branches. > > > > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> > > The logic is much improved in this version! A few smallish issues below: Glad to hear that! > > > --- > > tools/lib/bpf/xsk.c | 259 ++++++++++++++++++++++++++++++++++++-------- > > 1 file changed, 214 insertions(+), 45 deletions(-) > > > > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c > > index 526fc35c0b23..c75067f0035f 100644 > > --- a/tools/lib/bpf/xsk.c > > +++ b/tools/lib/bpf/xsk.c > > @@ -28,6 +28,7 @@ > > #include <sys/mman.h> > > #include <sys/socket.h> > > #include <sys/types.h> > > +#include <linux/if_link.h> > > > > #include "bpf.h" > > #include "libbpf.h" > > @@ -70,8 +71,10 @@ struct xsk_ctx { > > int ifindex; > > struct list_head list; > > int prog_fd; > > + int link_fd; > > int xsks_map_fd; > > char ifname[IFNAMSIZ]; > > + bool has_bpf_link; > > }; > > > > struct xsk_socket { > > @@ -409,7 +412,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) > > static const int log_buf_size = 16 * 1024; > > struct xsk_ctx *ctx = xsk->ctx; > > char log_buf[log_buf_size]; > > - int err, prog_fd; > > + int prog_fd; > > > > /* This is the fallback C-program: > > * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx) > > @@ -499,14 +502,43 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) > > return prog_fd; > > } > > > > - err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, prog_fd, > > - xsk->config.xdp_flags); > > + ctx->prog_fd = prog_fd; > > + return 0; > > +} > > + > > +static int xsk_create_bpf_link(struct xsk_socket *xsk) > > +{ > > + /* bpf_link only accepts XDP_FLAGS_MODES, but xsk->config.xdp_flags > > + * might have set XDP_FLAGS_UPDATE_IF_NOEXIST > > + */ > > + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, > > + .flags = (xsk->config.xdp_flags & XDP_FLAGS_MODES)); > > This will silently suppress any new flags as well; that's not a good > idea. Rather mask out the particular flag (UPDATE_IF_NOEXIST) and pass > everything else through so the kernel can reject invalid ones. I'd say it's fine as it matches the check: /* link supports only XDP mode flags */ if (link && (flags & ~XDP_FLAGS_MODES)) { NL_SET_ERR_MSG(extack, "Invalid XDP flags for BPF link attachment"); return -EINVAL; } from dev_xdp_attach() in net/core/dev.c ? > > > + struct xsk_ctx *ctx = xsk->ctx; > > + __u32 prog_id = 0; > > + int link_fd; > > + int err; > > + > > + err = bpf_get_link_xdp_id(ctx->ifindex, &prog_id, xsk->config.xdp_flags); > > if (err) { > > - close(prog_fd); > > + pr_warn("getting XDP prog id failed\n"); > > return err; > > } > > > > - ctx->prog_fd = prog_fd; > > + /* if there's a netlink-based XDP prog loaded on interface, bail out > > + * and ask user to do the removal by himself > > + */ > > + if (prog_id) { > > + pr_warn("Netlink-based XDP prog detected, please unload it in order to launch AF_XDP prog\n"); > > + return -EINVAL; > > + } > > + > > + link_fd = bpf_link_create(ctx->prog_fd, ctx->ifindex, BPF_XDP, &opts); > > + if (link_fd < 0) { > > + pr_warn("bpf_link_create failed: %s\n", strerror(errno)); > > + return link_fd; > > + } > > + > > + ctx->link_fd = link_fd; > > return 0; > > } > > > > @@ -625,7 +657,6 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk) > > close(fd); > > } > > > > - err = 0; > > if (ctx->xsks_map_fd == -1) > > err = -ENOENT; > > > > @@ -642,6 +673,97 @@ static int xsk_set_bpf_maps(struct xsk_socket *xsk) > > &xsk->fd, 0); > > } > > > > +static int xsk_link_lookup(int ifindex, __u32 *prog_id, int *link_fd) > > +{ > > + struct bpf_link_info link_info; > > + __u32 link_len; > > + __u32 id = 0; > > + int err; > > + int fd; > > + > > + while (true) { > > + err = bpf_link_get_next_id(id, &id); > > + if (err) { > > + if (errno == ENOENT) { > > + err = 0; > > + break; > > + } > > + pr_warn("can't get next link: %s\n", strerror(errno)); > > + break; > > + } > > + > > + fd = bpf_link_get_fd_by_id(id); > > + if (fd < 0) { > > + if (errno == ENOENT) > > + continue; > > + pr_warn("can't get link by id (%u): %s\n", id, strerror(errno)); > > + err = -errno; > > + break; > > + } > > + > > + link_len = sizeof(struct bpf_link_info); > > + memset(&link_info, 0, link_len); > > + err = bpf_obj_get_info_by_fd(fd, &link_info, &link_len); > > + if (err) { > > + pr_warn("can't get link info: %s\n", strerror(errno)); > > + close(fd); > > + break; > > + } > > + if (link_info.type == BPF_LINK_TYPE_XDP) { > > + if (link_info.xdp.ifindex == ifindex) { > > + *link_fd = fd; > > + if (prog_id) > > + *prog_id = link_info.prog_id; > > + break; > > + } > > + } > > + close(fd); > > + } > > + > > + return err; > > +} > > + > > +static bool xsk_probe_bpf_link(void) > > +{ > > + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, > > + .flags = XDP_FLAGS_SKB_MODE); > > + struct bpf_load_program_attr prog_attr; > > + struct bpf_insn insns[2] = { > > + BPF_MOV64_IMM(BPF_REG_0, XDP_PASS), > > + BPF_EXIT_INSN() > > + }; > > + int prog_fd, link_fd = -1; > > + int ifindex_lo = 1; > > + bool ret = false; > > + int err; > > + > > + err = xsk_link_lookup(ifindex_lo, NULL, &link_fd); > > + if (err) > > + return ret; > > + > > + if (link_fd >= 0) > > + return true; > > + > > + memset(&prog_attr, 0, sizeof(prog_attr)); > > + prog_attr.prog_type = BPF_PROG_TYPE_XDP; > > + prog_attr.insns = insns; > > + prog_attr.insns_cnt = ARRAY_SIZE(insns); > > + prog_attr.license = "GPL"; > > + > > + prog_fd = bpf_load_program_xattr(&prog_attr, NULL, 0); > > + if (prog_fd < 0) > > + return ret; > > + > > + link_fd = bpf_link_create(prog_fd, ifindex_lo, BPF_XDP, &opts); > > + if (link_fd >= 0) > > + ret = true; > > + > > + close(prog_fd); > > + close(link_fd); > > This potentially calls close() on an invalid link_fd... Will fix. > > > + > > + return ret; > > +} > > + > > static int xsk_create_xsk_struct(int ifindex, struct xsk_socket *xsk) > > { > > char ifname[IFNAMSIZ]; > > @@ -663,64 +785,108 @@ static int xsk_create_xsk_struct(int ifindex, struct xsk_socket *xsk) > > ctx->ifname[IFNAMSIZ - 1] = 0; > > > > xsk->ctx = ctx; > > + xsk->ctx->has_bpf_link = xsk_probe_bpf_link(); > > > > return 0; > > } > > > > -static int __xsk_setup_xdp_prog(struct xsk_socket *_xdp, > > - int *xsks_map_fd) > > +static int xsk_init_xdp_res(struct xsk_socket *xsk, > > + int *xsks_map_fd) > > { > > - struct xsk_socket *xsk = _xdp; > > struct xsk_ctx *ctx = xsk->ctx; > > - __u32 prog_id = 0; > > int err; > > > > - err = bpf_get_link_xdp_id(ctx->ifindex, &prog_id, > > - xsk->config.xdp_flags); > > + err = xsk_create_bpf_maps(xsk); > > if (err) > > return err; > > > > - if (!prog_id) { > > - err = xsk_create_bpf_maps(xsk); > > - if (err) > > - return err; > > + err = xsk_load_xdp_prog(xsk); > > + if (err) > > + goto err_load_xdp_prog; > > > > - err = xsk_load_xdp_prog(xsk); > > - if (err) { > > - goto err_load_xdp_prog; > > - } > > - } else { > > - ctx->prog_fd = bpf_prog_get_fd_by_id(prog_id); > > - if (ctx->prog_fd < 0) > > - return -errno; > > - err = xsk_lookup_bpf_maps(xsk); > > - if (err) { > > - close(ctx->prog_fd); > > - return err; > > - } > > - } > > + if (ctx->has_bpf_link) > > + err = xsk_create_bpf_link(xsk); > > + else > > + err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, ctx->prog_fd, > > + xsk->config.xdp_flags); > > > > - if (xsk->rx) { > > - err = xsk_set_bpf_maps(xsk); > > - if (err) { > > - if (!prog_id) { > > - goto err_set_bpf_maps; > > - } else { > > - close(ctx->prog_fd); > > - return err; > > - } > > - } > > - } > > - if (xsks_map_fd) > > - *xsks_map_fd = ctx->xsks_map_fd; > > + if (err) > > + goto err_atach_xdp_prog; > > s/atach/attach/ Whoops :) > > -Toke >
Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes: > On Mon, Mar 29, 2021 at 01:05:44PM +0200, Toke Høiland-Jørgensen wrote: >> Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes: >> >> > Currently, if there are multiple xdpsock instances running on a single >> > interface and in case one of the instances is terminated, the rest of >> > them are left in an inoperable state due to the fact of unloaded XDP >> > prog from interface. >> > >> > Consider the scenario below: >> > >> > // load xdp prog and xskmap and add entry to xskmap at idx 10 >> > $ sudo ./xdpsock -i ens801f0 -t -q 10 >> > >> > // add entry to xskmap at idx 11 >> > $ sudo ./xdpsock -i ens801f0 -t -q 11 >> > >> > terminate one of the processes and another one is unable to work due to >> > the fact that the XDP prog was unloaded from interface. >> > >> > To address that, step away from setting bpf prog in favour of bpf_link. >> > This means that refcounting of BPF resources will be done automatically >> > by bpf_link itself. >> > >> > Provide backward compatibility by checking if underlying system is >> > bpf_link capable. Do this by looking up/creating bpf_link on loopback >> > device. If it failed in any way, stick with netlink-based XDP prog. >> > therwise, use bpf_link-based logic. >> > >> > When setting up BPF resources during xsk socket creation, check whether >> > bpf_link for a given ifindex already exists via set of calls to >> > bpf_link_get_next_id -> bpf_link_get_fd_by_id -> bpf_obj_get_info_by_fd >> > and comparing the ifindexes from bpf_link and xsk socket. >> > >> > For case where resources exist but they are not AF_XDP related, bail out >> > and ask user to remove existing prog and then retry. >> > >> > Lastly, do a bit of refactoring within __xsk_setup_xdp_prog and pull out >> > existing code branches based on prog_id value onto separate functions >> > that are responsible for resource initialization if prog_id was 0 and >> > for lookup existing resources for non-zero prog_id as that implies that >> > XDP program is present on the underlying net device. This in turn makes >> > it easier to follow, especially the teardown part of both branches. >> > >> > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> >> >> The logic is much improved in this version! A few smallish issues below: > > Glad to hear that! > >> >> > --- >> > tools/lib/bpf/xsk.c | 259 ++++++++++++++++++++++++++++++++++++-------- >> > 1 file changed, 214 insertions(+), 45 deletions(-) >> > >> > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c >> > index 526fc35c0b23..c75067f0035f 100644 >> > --- a/tools/lib/bpf/xsk.c >> > +++ b/tools/lib/bpf/xsk.c >> > @@ -28,6 +28,7 @@ >> > #include <sys/mman.h> >> > #include <sys/socket.h> >> > #include <sys/types.h> >> > +#include <linux/if_link.h> >> > >> > #include "bpf.h" >> > #include "libbpf.h" >> > @@ -70,8 +71,10 @@ struct xsk_ctx { >> > int ifindex; >> > struct list_head list; >> > int prog_fd; >> > + int link_fd; >> > int xsks_map_fd; >> > char ifname[IFNAMSIZ]; >> > + bool has_bpf_link; >> > }; >> > >> > struct xsk_socket { >> > @@ -409,7 +412,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) >> > static const int log_buf_size = 16 * 1024; >> > struct xsk_ctx *ctx = xsk->ctx; >> > char log_buf[log_buf_size]; >> > - int err, prog_fd; >> > + int prog_fd; >> > >> > /* This is the fallback C-program: >> > * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx) >> > @@ -499,14 +502,43 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) >> > return prog_fd; >> > } >> > >> > - err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, prog_fd, >> > - xsk->config.xdp_flags); >> > + ctx->prog_fd = prog_fd; >> > + return 0; >> > +} >> > + >> > +static int xsk_create_bpf_link(struct xsk_socket *xsk) >> > +{ >> > + /* bpf_link only accepts XDP_FLAGS_MODES, but xsk->config.xdp_flags >> > + * might have set XDP_FLAGS_UPDATE_IF_NOEXIST >> > + */ >> > + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, >> > + .flags = (xsk->config.xdp_flags & XDP_FLAGS_MODES)); >> >> This will silently suppress any new flags as well; that's not a good >> idea. Rather mask out the particular flag (UPDATE_IF_NOEXIST) and pass >> everything else through so the kernel can reject invalid ones. > > I'd say it's fine as it matches the check: > > /* link supports only XDP mode flags */ > if (link && (flags & ~XDP_FLAGS_MODES)) { > NL_SET_ERR_MSG(extack, "Invalid XDP flags for BPF link attachment"); > return -EINVAL; > } > > from dev_xdp_attach() in net/core/dev.c ? Yeah, it does today. But what happens when the kernel learns to accept a new flag? Also, you're masking the error on an invalid flag. If, in the future, the kernel learns to handle a new flag, that check in the kernel will change to accept that new flag. But if userspace tries to pass that to and old kernel, they'll get back an EINVAL. This can be used to detect whether the kernel doesn't support the flag, and can if not, userspace can fall back and do something different. Whereas with your code, you're just silently zeroing out the invalid flag, so the caller will have no way to detect whether the flag works or not... -Toke
On Mon, Mar 29, 2021 at 04:09:33PM +0200, Toke Høiland-Jørgensen wrote: > Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes: > > > On Mon, Mar 29, 2021 at 01:05:44PM +0200, Toke Høiland-Jørgensen wrote: > >> Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes: > >> > >> > Currently, if there are multiple xdpsock instances running on a single > >> > interface and in case one of the instances is terminated, the rest of > >> > them are left in an inoperable state due to the fact of unloaded XDP > >> > prog from interface. > >> > > >> > Consider the scenario below: > >> > > >> > // load xdp prog and xskmap and add entry to xskmap at idx 10 > >> > $ sudo ./xdpsock -i ens801f0 -t -q 10 > >> > > >> > // add entry to xskmap at idx 11 > >> > $ sudo ./xdpsock -i ens801f0 -t -q 11 > >> > > >> > terminate one of the processes and another one is unable to work due to > >> > the fact that the XDP prog was unloaded from interface. > >> > > >> > To address that, step away from setting bpf prog in favour of bpf_link. > >> > This means that refcounting of BPF resources will be done automatically > >> > by bpf_link itself. > >> > > >> > Provide backward compatibility by checking if underlying system is > >> > bpf_link capable. Do this by looking up/creating bpf_link on loopback > >> > device. If it failed in any way, stick with netlink-based XDP prog. > >> > therwise, use bpf_link-based logic. > >> > > >> > When setting up BPF resources during xsk socket creation, check whether > >> > bpf_link for a given ifindex already exists via set of calls to > >> > bpf_link_get_next_id -> bpf_link_get_fd_by_id -> bpf_obj_get_info_by_fd > >> > and comparing the ifindexes from bpf_link and xsk socket. > >> > > >> > For case where resources exist but they are not AF_XDP related, bail out > >> > and ask user to remove existing prog and then retry. > >> > > >> > Lastly, do a bit of refactoring within __xsk_setup_xdp_prog and pull out > >> > existing code branches based on prog_id value onto separate functions > >> > that are responsible for resource initialization if prog_id was 0 and > >> > for lookup existing resources for non-zero prog_id as that implies that > >> > XDP program is present on the underlying net device. This in turn makes > >> > it easier to follow, especially the teardown part of both branches. > >> > > >> > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> > >> > >> The logic is much improved in this version! A few smallish issues below: > > > > Glad to hear that! > > > >> > >> > --- > >> > tools/lib/bpf/xsk.c | 259 ++++++++++++++++++++++++++++++++++++-------- > >> > 1 file changed, 214 insertions(+), 45 deletions(-) > >> > > >> > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c > >> > index 526fc35c0b23..c75067f0035f 100644 > >> > --- a/tools/lib/bpf/xsk.c > >> > +++ b/tools/lib/bpf/xsk.c > >> > @@ -28,6 +28,7 @@ > >> > #include <sys/mman.h> > >> > #include <sys/socket.h> > >> > #include <sys/types.h> > >> > +#include <linux/if_link.h> > >> > > >> > #include "bpf.h" > >> > #include "libbpf.h" > >> > @@ -70,8 +71,10 @@ struct xsk_ctx { > >> > int ifindex; > >> > struct list_head list; > >> > int prog_fd; > >> > + int link_fd; > >> > int xsks_map_fd; > >> > char ifname[IFNAMSIZ]; > >> > + bool has_bpf_link; > >> > }; > >> > > >> > struct xsk_socket { > >> > @@ -409,7 +412,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) > >> > static const int log_buf_size = 16 * 1024; > >> > struct xsk_ctx *ctx = xsk->ctx; > >> > char log_buf[log_buf_size]; > >> > - int err, prog_fd; > >> > + int prog_fd; > >> > > >> > /* This is the fallback C-program: > >> > * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx) > >> > @@ -499,14 +502,43 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) > >> > return prog_fd; > >> > } > >> > > >> > - err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, prog_fd, > >> > - xsk->config.xdp_flags); > >> > + ctx->prog_fd = prog_fd; > >> > + return 0; > >> > +} > >> > + > >> > +static int xsk_create_bpf_link(struct xsk_socket *xsk) > >> > +{ > >> > + /* bpf_link only accepts XDP_FLAGS_MODES, but xsk->config.xdp_flags > >> > + * might have set XDP_FLAGS_UPDATE_IF_NOEXIST > >> > + */ > >> > + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, > >> > + .flags = (xsk->config.xdp_flags & XDP_FLAGS_MODES)); > >> > >> This will silently suppress any new flags as well; that's not a good > >> idea. Rather mask out the particular flag (UPDATE_IF_NOEXIST) and pass > >> everything else through so the kernel can reject invalid ones. > > > > I'd say it's fine as it matches the check: > > > > /* link supports only XDP mode flags */ > > if (link && (flags & ~XDP_FLAGS_MODES)) { > > NL_SET_ERR_MSG(extack, "Invalid XDP flags for BPF link attachment"); > > return -EINVAL; > > } > > > > from dev_xdp_attach() in net/core/dev.c ? > > Yeah, it does today. But what happens when the kernel learns to accept a > new flag? > > Also, you're masking the error on an invalid flag. If, in the future, > the kernel learns to handle a new flag, that check in the kernel will > change to accept that new flag. But if userspace tries to pass that to > and old kernel, they'll get back an EINVAL. This can be used to detect > whether the kernel doesn't support the flag, and can if not, userspace > can fall back and do something different. > > Whereas with your code, you're just silently zeroing out the invalid > flag, so the caller will have no way to detect whether the flag works > or not... I'd rather worry about such feature detection once a new flag is in place and this code would actually care about :) but that's me. I feel like stick has two ends in this case - if we introduce a new flag that would be out of the bpf_link's interest (the kernel part), then we will have to come back here and explicitly mask it out, just like you propose to do so with UPDATE_IF_NOEXIST right now. What I'm saying is that we need to mask out the FLAGS_REPLACE as well. Current code took care of that. So, to move this forward, I can do: diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c index c75067f0035f..95da0e19f4a5 100644 --- a/tools/lib/bpf/xsk.c +++ b/tools/lib/bpf/xsk.c @@ -508,11 +508,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) static int xsk_create_bpf_link(struct xsk_socket *xsk) { - /* bpf_link only accepts XDP_FLAGS_MODES, but xsk->config.xdp_flags - * might have set XDP_FLAGS_UPDATE_IF_NOEXIST - */ - DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, - .flags = (xsk->config.xdp_flags & XDP_FLAGS_MODES)); + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts); struct xsk_ctx *ctx = xsk->ctx; __u32 prog_id = 0; int link_fd; @@ -532,6 +528,8 @@ static int xsk_create_bpf_link(struct xsk_socket *xsk) return -EINVAL; } + opts.flags = xsk->config.xdp_flags & ~(XDP_FLAGS_UPDATE_IF_NOEXIST | XDP_FLAGS_REPLACE); + link_fd = bpf_link_create(ctx->prog_fd, ctx->ifindex, BPF_XDP, &opts); if (link_fd < 0) { pr_warn("bpf_link_create failed: %s\n", strerror(errno)); > > -Toke >
Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes: > On Mon, Mar 29, 2021 at 04:09:33PM +0200, Toke Høiland-Jørgensen wrote: >> Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes: >> >> > On Mon, Mar 29, 2021 at 01:05:44PM +0200, Toke Høiland-Jørgensen wrote: >> >> Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes: >> >> >> >> > Currently, if there are multiple xdpsock instances running on a single >> >> > interface and in case one of the instances is terminated, the rest of >> >> > them are left in an inoperable state due to the fact of unloaded XDP >> >> > prog from interface. >> >> > >> >> > Consider the scenario below: >> >> > >> >> > // load xdp prog and xskmap and add entry to xskmap at idx 10 >> >> > $ sudo ./xdpsock -i ens801f0 -t -q 10 >> >> > >> >> > // add entry to xskmap at idx 11 >> >> > $ sudo ./xdpsock -i ens801f0 -t -q 11 >> >> > >> >> > terminate one of the processes and another one is unable to work due to >> >> > the fact that the XDP prog was unloaded from interface. >> >> > >> >> > To address that, step away from setting bpf prog in favour of bpf_link. >> >> > This means that refcounting of BPF resources will be done automatically >> >> > by bpf_link itself. >> >> > >> >> > Provide backward compatibility by checking if underlying system is >> >> > bpf_link capable. Do this by looking up/creating bpf_link on loopback >> >> > device. If it failed in any way, stick with netlink-based XDP prog. >> >> > therwise, use bpf_link-based logic. >> >> > >> >> > When setting up BPF resources during xsk socket creation, check whether >> >> > bpf_link for a given ifindex already exists via set of calls to >> >> > bpf_link_get_next_id -> bpf_link_get_fd_by_id -> bpf_obj_get_info_by_fd >> >> > and comparing the ifindexes from bpf_link and xsk socket. >> >> > >> >> > For case where resources exist but they are not AF_XDP related, bail out >> >> > and ask user to remove existing prog and then retry. >> >> > >> >> > Lastly, do a bit of refactoring within __xsk_setup_xdp_prog and pull out >> >> > existing code branches based on prog_id value onto separate functions >> >> > that are responsible for resource initialization if prog_id was 0 and >> >> > for lookup existing resources for non-zero prog_id as that implies that >> >> > XDP program is present on the underlying net device. This in turn makes >> >> > it easier to follow, especially the teardown part of both branches. >> >> > >> >> > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> >> >> >> >> The logic is much improved in this version! A few smallish issues below: >> > >> > Glad to hear that! >> > >> >> >> >> > --- >> >> > tools/lib/bpf/xsk.c | 259 ++++++++++++++++++++++++++++++++++++-------- >> >> > 1 file changed, 214 insertions(+), 45 deletions(-) >> >> > >> >> > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c >> >> > index 526fc35c0b23..c75067f0035f 100644 >> >> > --- a/tools/lib/bpf/xsk.c >> >> > +++ b/tools/lib/bpf/xsk.c >> >> > @@ -28,6 +28,7 @@ >> >> > #include <sys/mman.h> >> >> > #include <sys/socket.h> >> >> > #include <sys/types.h> >> >> > +#include <linux/if_link.h> >> >> > >> >> > #include "bpf.h" >> >> > #include "libbpf.h" >> >> > @@ -70,8 +71,10 @@ struct xsk_ctx { >> >> > int ifindex; >> >> > struct list_head list; >> >> > int prog_fd; >> >> > + int link_fd; >> >> > int xsks_map_fd; >> >> > char ifname[IFNAMSIZ]; >> >> > + bool has_bpf_link; >> >> > }; >> >> > >> >> > struct xsk_socket { >> >> > @@ -409,7 +412,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) >> >> > static const int log_buf_size = 16 * 1024; >> >> > struct xsk_ctx *ctx = xsk->ctx; >> >> > char log_buf[log_buf_size]; >> >> > - int err, prog_fd; >> >> > + int prog_fd; >> >> > >> >> > /* This is the fallback C-program: >> >> > * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx) >> >> > @@ -499,14 +502,43 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) >> >> > return prog_fd; >> >> > } >> >> > >> >> > - err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, prog_fd, >> >> > - xsk->config.xdp_flags); >> >> > + ctx->prog_fd = prog_fd; >> >> > + return 0; >> >> > +} >> >> > + >> >> > +static int xsk_create_bpf_link(struct xsk_socket *xsk) >> >> > +{ >> >> > + /* bpf_link only accepts XDP_FLAGS_MODES, but xsk->config.xdp_flags >> >> > + * might have set XDP_FLAGS_UPDATE_IF_NOEXIST >> >> > + */ >> >> > + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, >> >> > + .flags = (xsk->config.xdp_flags & XDP_FLAGS_MODES)); >> >> >> >> This will silently suppress any new flags as well; that's not a good >> >> idea. Rather mask out the particular flag (UPDATE_IF_NOEXIST) and pass >> >> everything else through so the kernel can reject invalid ones. >> > >> > I'd say it's fine as it matches the check: >> > >> > /* link supports only XDP mode flags */ >> > if (link && (flags & ~XDP_FLAGS_MODES)) { >> > NL_SET_ERR_MSG(extack, "Invalid XDP flags for BPF link attachment"); >> > return -EINVAL; >> > } >> > >> > from dev_xdp_attach() in net/core/dev.c ? >> >> Yeah, it does today. But what happens when the kernel learns to accept a >> new flag? >> >> Also, you're masking the error on an invalid flag. If, in the future, >> the kernel learns to handle a new flag, that check in the kernel will >> change to accept that new flag. But if userspace tries to pass that to >> and old kernel, they'll get back an EINVAL. This can be used to detect >> whether the kernel doesn't support the flag, and can if not, userspace >> can fall back and do something different. >> >> Whereas with your code, you're just silently zeroing out the invalid >> flag, so the caller will have no way to detect whether the flag works >> or not... > > I'd rather worry about such feature detection once a new flag is in place > and this code would actually care about :) but that's me. > > I feel like stick has two ends in this case - if we introduce a new flag > that would be out of the bpf_link's interest (the kernel part), then we > will have to come back here and explicitly mask it out, just like you > propose to do so with UPDATE_IF_NOEXIST right now. Well I'd rather err on the side of throwing errors for new flags than on silently suppressing them :) (The partial sharing of flags between netlink and bpf_link is a bit odd in any case, but that's another discussion) > What I'm saying is that we need to mask out the FLAGS_REPLACE as well. > Current code took care of that. So, to move this forward, I can do: > > diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c > index c75067f0035f..95da0e19f4a5 100644 > --- a/tools/lib/bpf/xsk.c > +++ b/tools/lib/bpf/xsk.c > @@ -508,11 +508,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) > > static int xsk_create_bpf_link(struct xsk_socket *xsk) > { > - /* bpf_link only accepts XDP_FLAGS_MODES, but xsk->config.xdp_flags > - * might have set XDP_FLAGS_UPDATE_IF_NOEXIST > - */ > - DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, > - .flags = (xsk->config.xdp_flags & XDP_FLAGS_MODES)); > + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts); > struct xsk_ctx *ctx = xsk->ctx; > __u32 prog_id = 0; > int link_fd; > @@ -532,6 +528,8 @@ static int xsk_create_bpf_link(struct xsk_socket *xsk) > return -EINVAL; > } > > + opts.flags = xsk->config.xdp_flags & ~(XDP_FLAGS_UPDATE_IF_NOEXIST | XDP_FLAGS_REPLACE); > + > link_fd = bpf_link_create(ctx->prog_fd, ctx->ifindex, BPF_XDP, &opts); > if (link_fd < 0) { > pr_warn("bpf_link_create failed: %s\n", strerror(errno)); Yup, this works for me! :) -Toke
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c index 526fc35c0b23..c75067f0035f 100644 --- a/tools/lib/bpf/xsk.c +++ b/tools/lib/bpf/xsk.c @@ -28,6 +28,7 @@ #include <sys/mman.h> #include <sys/socket.h> #include <sys/types.h> +#include <linux/if_link.h> #include "bpf.h" #include "libbpf.h" @@ -70,8 +71,10 @@ struct xsk_ctx { int ifindex; struct list_head list; int prog_fd; + int link_fd; int xsks_map_fd; char ifname[IFNAMSIZ]; + bool has_bpf_link; }; struct xsk_socket { @@ -409,7 +412,7 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) static const int log_buf_size = 16 * 1024; struct xsk_ctx *ctx = xsk->ctx; char log_buf[log_buf_size]; - int err, prog_fd; + int prog_fd; /* This is the fallback C-program: * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx) @@ -499,14 +502,43 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk) return prog_fd; } - err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, prog_fd, - xsk->config.xdp_flags); + ctx->prog_fd = prog_fd; + return 0; +} + +static int xsk_create_bpf_link(struct xsk_socket *xsk) +{ + /* bpf_link only accepts XDP_FLAGS_MODES, but xsk->config.xdp_flags + * might have set XDP_FLAGS_UPDATE_IF_NOEXIST + */ + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, + .flags = (xsk->config.xdp_flags & XDP_FLAGS_MODES)); + struct xsk_ctx *ctx = xsk->ctx; + __u32 prog_id = 0; + int link_fd; + int err; + + err = bpf_get_link_xdp_id(ctx->ifindex, &prog_id, xsk->config.xdp_flags); if (err) { - close(prog_fd); + pr_warn("getting XDP prog id failed\n"); return err; } - ctx->prog_fd = prog_fd; + /* if there's a netlink-based XDP prog loaded on interface, bail out + * and ask user to do the removal by himself + */ + if (prog_id) { + pr_warn("Netlink-based XDP prog detected, please unload it in order to launch AF_XDP prog\n"); + return -EINVAL; + } + + link_fd = bpf_link_create(ctx->prog_fd, ctx->ifindex, BPF_XDP, &opts); + if (link_fd < 0) { + pr_warn("bpf_link_create failed: %s\n", strerror(errno)); + return link_fd; + } + + ctx->link_fd = link_fd; return 0; } @@ -625,7 +657,6 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk) close(fd); } - err = 0; if (ctx->xsks_map_fd == -1) err = -ENOENT; @@ -642,6 +673,97 @@ static int xsk_set_bpf_maps(struct xsk_socket *xsk) &xsk->fd, 0); } +static int xsk_link_lookup(int ifindex, __u32 *prog_id, int *link_fd) +{ + struct bpf_link_info link_info; + __u32 link_len; + __u32 id = 0; + int err; + int fd; + + while (true) { + err = bpf_link_get_next_id(id, &id); + if (err) { + if (errno == ENOENT) { + err = 0; + break; + } + pr_warn("can't get next link: %s\n", strerror(errno)); + break; + } + + fd = bpf_link_get_fd_by_id(id); + if (fd < 0) { + if (errno == ENOENT) + continue; + pr_warn("can't get link by id (%u): %s\n", id, strerror(errno)); + err = -errno; + break; + } + + link_len = sizeof(struct bpf_link_info); + memset(&link_info, 0, link_len); + err = bpf_obj_get_info_by_fd(fd, &link_info, &link_len); + if (err) { + pr_warn("can't get link info: %s\n", strerror(errno)); + close(fd); + break; + } + if (link_info.type == BPF_LINK_TYPE_XDP) { + if (link_info.xdp.ifindex == ifindex) { + *link_fd = fd; + if (prog_id) + *prog_id = link_info.prog_id; + break; + } + } + close(fd); + } + + return err; +} + +static bool xsk_probe_bpf_link(void) +{ + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts, + .flags = XDP_FLAGS_SKB_MODE); + struct bpf_load_program_attr prog_attr; + struct bpf_insn insns[2] = { + BPF_MOV64_IMM(BPF_REG_0, XDP_PASS), + BPF_EXIT_INSN() + }; + int prog_fd, link_fd = -1; + int ifindex_lo = 1; + bool ret = false; + int err; + + err = xsk_link_lookup(ifindex_lo, NULL, &link_fd); + if (err) + return ret; + + if (link_fd >= 0) + return true; + + memset(&prog_attr, 0, sizeof(prog_attr)); + prog_attr.prog_type = BPF_PROG_TYPE_XDP; + prog_attr.insns = insns; + prog_attr.insns_cnt = ARRAY_SIZE(insns); + prog_attr.license = "GPL"; + + prog_fd = bpf_load_program_xattr(&prog_attr, NULL, 0); + if (prog_fd < 0) + return ret; + + link_fd = bpf_link_create(prog_fd, ifindex_lo, BPF_XDP, &opts); + if (link_fd >= 0) + ret = true; + + close(prog_fd); + close(link_fd); + + return ret; +} + static int xsk_create_xsk_struct(int ifindex, struct xsk_socket *xsk) { char ifname[IFNAMSIZ]; @@ -663,64 +785,108 @@ static int xsk_create_xsk_struct(int ifindex, struct xsk_socket *xsk) ctx->ifname[IFNAMSIZ - 1] = 0; xsk->ctx = ctx; + xsk->ctx->has_bpf_link = xsk_probe_bpf_link(); return 0; } -static int __xsk_setup_xdp_prog(struct xsk_socket *_xdp, - int *xsks_map_fd) +static int xsk_init_xdp_res(struct xsk_socket *xsk, + int *xsks_map_fd) { - struct xsk_socket *xsk = _xdp; struct xsk_ctx *ctx = xsk->ctx; - __u32 prog_id = 0; int err; - err = bpf_get_link_xdp_id(ctx->ifindex, &prog_id, - xsk->config.xdp_flags); + err = xsk_create_bpf_maps(xsk); if (err) return err; - if (!prog_id) { - err = xsk_create_bpf_maps(xsk); - if (err) - return err; + err = xsk_load_xdp_prog(xsk); + if (err) + goto err_load_xdp_prog; - err = xsk_load_xdp_prog(xsk); - if (err) { - goto err_load_xdp_prog; - } - } else { - ctx->prog_fd = bpf_prog_get_fd_by_id(prog_id); - if (ctx->prog_fd < 0) - return -errno; - err = xsk_lookup_bpf_maps(xsk); - if (err) { - close(ctx->prog_fd); - return err; - } - } + if (ctx->has_bpf_link) + err = xsk_create_bpf_link(xsk); + else + err = bpf_set_link_xdp_fd(xsk->ctx->ifindex, ctx->prog_fd, + xsk->config.xdp_flags); - if (xsk->rx) { - err = xsk_set_bpf_maps(xsk); - if (err) { - if (!prog_id) { - goto err_set_bpf_maps; - } else { - close(ctx->prog_fd); - return err; - } - } - } - if (xsks_map_fd) - *xsks_map_fd = ctx->xsks_map_fd; + if (err) + goto err_atach_xdp_prog; - return 0; + if (!xsk->rx) + return err; + + err = xsk_set_bpf_maps(xsk); + if (err) + goto err_set_bpf_maps; + + return err; err_set_bpf_maps: + if (ctx->has_bpf_link) + close(ctx->link_fd); + else + bpf_set_link_xdp_fd(ctx->ifindex, -1, 0); +err_atach_xdp_prog: close(ctx->prog_fd); - bpf_set_link_xdp_fd(ctx->ifindex, -1, 0); err_load_xdp_prog: xsk_delete_bpf_maps(xsk); + return err; +} + +static int xsk_lookup_xdp_res(struct xsk_socket *xsk, int *xsks_map_fd, int prog_id) +{ + struct xsk_ctx *ctx = xsk->ctx; + int err; + + ctx->prog_fd = bpf_prog_get_fd_by_id(prog_id); + if (ctx->prog_fd < 0) { + err = -errno; + goto err_prog_fd; + } + err = xsk_lookup_bpf_maps(xsk); + if (err) + goto err_lookup_maps; + + if (!xsk->rx) + return err; + + err = xsk_set_bpf_maps(xsk); + if (err) + goto err_set_maps; + + return err; + +err_set_maps: + close(ctx->xsks_map_fd); +err_lookup_maps: + close(ctx->prog_fd); +err_prog_fd: + if (ctx->has_bpf_link) + close(ctx->link_fd); + return err; +} + +static int __xsk_setup_xdp_prog(struct xsk_socket *_xdp, int *xsks_map_fd) +{ + struct xsk_socket *xsk = _xdp; + struct xsk_ctx *ctx = xsk->ctx; + __u32 prog_id = 0; + int err; + + if (ctx->has_bpf_link) + err = xsk_link_lookup(ctx->ifindex, &prog_id, &ctx->link_fd); + else + err = bpf_get_link_xdp_id(ctx->ifindex, &prog_id, xsk->config.xdp_flags); + + if (err) + return err; + + err = !prog_id ? xsk_init_xdp_res(xsk, xsks_map_fd) : + xsk_lookup_xdp_res(xsk, xsks_map_fd, prog_id); + + if (!err && xsks_map_fd) + *xsks_map_fd = ctx->xsks_map_fd; return err; } @@ -898,6 +1064,7 @@ int xsk_socket__create_shared(struct xsk_socket **xsk_ptr, } } xsk->ctx = ctx; + xsk->ctx->has_bpf_link = xsk_probe_bpf_link(); if (rx) { err = setsockopt(xsk->fd, SOL_XDP, XDP_RX_RING, @@ -1054,6 +1221,8 @@ void xsk_socket__delete(struct xsk_socket *xsk) if (ctx->prog_fd != -1) { xsk_delete_bpf_maps(xsk); close(ctx->prog_fd); + if (ctx->has_bpf_link) + close(ctx->link_fd); } err = xsk_get_mmap_offsets(xsk->fd, &off);
Currently, if there are multiple xdpsock instances running on a single interface and in case one of the instances is terminated, the rest of them are left in an inoperable state due to the fact of unloaded XDP prog from interface. Consider the scenario below: // load xdp prog and xskmap and add entry to xskmap at idx 10 $ sudo ./xdpsock -i ens801f0 -t -q 10 // add entry to xskmap at idx 11 $ sudo ./xdpsock -i ens801f0 -t -q 11 terminate one of the processes and another one is unable to work due to the fact that the XDP prog was unloaded from interface. To address that, step away from setting bpf prog in favour of bpf_link. This means that refcounting of BPF resources will be done automatically by bpf_link itself. Provide backward compatibility by checking if underlying system is bpf_link capable. Do this by looking up/creating bpf_link on loopback device. If it failed in any way, stick with netlink-based XDP prog. therwise, use bpf_link-based logic. When setting up BPF resources during xsk socket creation, check whether bpf_link for a given ifindex already exists via set of calls to bpf_link_get_next_id -> bpf_link_get_fd_by_id -> bpf_obj_get_info_by_fd and comparing the ifindexes from bpf_link and xsk socket. For case where resources exist but they are not AF_XDP related, bail out and ask user to remove existing prog and then retry. Lastly, do a bit of refactoring within __xsk_setup_xdp_prog and pull out existing code branches based on prog_id value onto separate functions that are responsible for resource initialization if prog_id was 0 and for lookup existing resources for non-zero prog_id as that implies that XDP program is present on the underlying net device. This in turn makes it easier to follow, especially the teardown part of both branches. Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> --- tools/lib/bpf/xsk.c | 259 ++++++++++++++++++++++++++++++++++++-------- 1 file changed, 214 insertions(+), 45 deletions(-)