From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer via iovisor-dev Subject: Re: bpf_redirect_map not working after tail call Date: Mon, 4 Jun 2018 13:04:35 +0200 Message-ID: <20180604130435.27d29431@redhat.com> References: <319a775a-4913-1e58-c0dd-f3d6e3f56d9e@polito.it> Reply-To: Jesper Dangaard Brouer Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: "netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" To: iovisor-dev , Daniel Borkmann Return-path: In-Reply-To: <319a775a-4913-1e58-c0dd-f3d6e3f56d9e-8RLafaVCWuNeoWH0uzbU5w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iovisor-dev-bounces-9jONkmmOlFHEE9lA1F8Ukti2O/JbrIOy@public.gmane.org Errors-To: iovisor-dev-bounces-9jONkmmOlFHEE9lA1F8Ukti2O/JbrIOy@public.gmane.org List-Id: netdev.vger.kernel.org On Fri, 1 Jun 2018 14:15:58 +0200 Sebastiano Miano via iovisor-dev wrote: > Dear all, > > We have noticed that the bpf_redirect_map returns an error when it is > called after a tail call. > The xdp_redirect_map program (under sample/bpf) works fine, but if we > modify it as shown in the following diff, it doesn't work anymore. > I have debugged it with the xdp_monitor application and the error > returned is EFAULT. > Is this a known issue? Am I doing something wrong? Argh, this is likely an issue/bug due to the check xdp_map_invalid(), that was introduced in commit 7c3001313396 ("bpf: fix ri->map_owner pointer on bpf_prog_realloc"). To Daniel, I don't know how to solve this, could you give some advice? static inline bool xdp_map_invalid(const struct bpf_prog *xdp_prog, unsigned long aux) { return (unsigned long)xdp_prog->aux != aux; } static int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp, struct bpf_prog *xdp_prog) { struct redirect_info *ri = this_cpu_ptr(&redirect_info); unsigned long map_owner = ri->map_owner; struct bpf_map *map = ri->map; u32 index = ri->ifindex; void *fwd = NULL; int err; [...] if (unlikely(xdp_map_invalid(xdp_prog, map_owner))) { err = -EFAULT; map = NULL; goto err; } [...] > P.S. I have tested the program with the latest bpf-next kernel. > > ------------ > > diff --git a/samples/bpf/xdp_redirect_map_kern.c > b/samples/bpf/xdp_redirect_map_kern.c > index 740a529..bf1275a 100644 > --- a/samples/bpf/xdp_redirect_map_kern.c > +++ b/samples/bpf/xdp_redirect_map_kern.c > @@ -36,6 +36,13 @@ struct bpf_map_def SEC("maps") rxcnt = { > .max_entries = 1, > }; > > +struct bpf_map_def SEC("maps") prog_table = { > + .type = BPF_MAP_TYPE_PROG_ARRAY, > + .key_size = sizeof(int), > + .value_size = sizeof(int), > + .max_entries = 32, > +}; > + > static void swap_src_dst_mac(void *data) > { > unsigned short *p = data; > @@ -89,4 +96,15 @@ int xdp_redirect_dummy_prog(struct xdp_md *ctx) > return XDP_PASS; > } > > +/* Entry point */ > +SEC("xdp_redirect_entry_point") > +int xdp_redirect_entry_point_prog(struct xdp_md *ctx) > +{ > + //char fmt[] = "xdp_redirect_entry_point\n"; > + //bpf_trace_printk(fmt, sizeof(fmt)); > + bpf_tail_call(ctx, &prog_table, 0); > + // Tail call failed > + return XDP_DROP; > +} > + > char _license[] SEC("license") = "GPL"; > diff --git a/samples/bpf/xdp_redirect_map_user.c > b/samples/bpf/xdp_redirect_map_user.c > index 4445e76..b2d2059 100644 > --- a/samples/bpf/xdp_redirect_map_user.c > +++ b/samples/bpf/xdp_redirect_map_user.c > @@ -120,7 +120,13 @@ int main(int argc, char **argv) > return 1; > } > > - if (bpf_set_link_xdp_fd(ifindex_in, prog_fd[0], xdp_flags) < 0) { > + ret = bpf_map_update_elem(map_fd[2], &key, &prog_fd[0], 0); > + if (ret) { > + perror("bpf_update_elem"); > + goto out; > + } > + > + if (bpf_set_link_xdp_fd(ifindex_in, prog_fd[2], xdp_flags) < 0) { > printf("ERROR: link set xdp fd failed on %d\n", ifindex_in); > return 1; > } > _______________________________________________ > iovisor-dev mailing list > iovisor-dev-9jONkmmOlFHEE9lA1F8Ukti2O/JbrIOy@public.gmane.org > https://lists.iovisor.org/mailman/listinfo/iovisor-dev -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer