libbpf: add function to setup XDP

Most of the code is taken from set_link_xdp_fd() in bpf_load.c and
slightly modified to be library compliant.

Signed-off-by: Eric Leblond <eric@regit.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 122 insertions, 0 deletions

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 5128677e4117..bf2772566240 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -25,6 +25,12 @@
 #include <asm/unistd.h>
 #include <linux/bpf.h>
 #include "bpf.h"
+#include "libbpf.h"
+#include "nlattr.h"
+#include <linux/rtnetlink.h>
+#include <linux/if_link.h>
+#include <sys/socket.h>
+#include <errno.h>
 
 /*
  * When building perf, unistd.h is overridden. __NR_bpf is
@@ -46,7 +52,9 @@
 # endif
 #endif
 
+#ifndef min
 #define min(x, y) ((x) < (y) ? (x) : (y))
+#endif
 
 static inline __u64 ptr_to_u64(const void *ptr)
 {
@@ -413,3 +421,117 @@ int bpf_obj_get_info_by_fd(int prog_fd, void *info, __u32 *info_len)
 
         return err;
 }
+
+int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
+{
+        struct sockaddr_nl sa;
+        int sock, seq = 0, len, ret = -1;
+        char buf[4096];
+        struct nlattr *nla, *nla_xdp;
+        struct {
+                struct nlmsghdr  nh;
+                struct ifinfomsg ifinfo;
+                char             attrbuf[64];
+        } req;
+        struct nlmsghdr *nh;
+        struct nlmsgerr *err;
+        socklen_t addrlen;
+
+        memset(&sa, 0, sizeof(sa));
+        sa.nl_family = AF_NETLINK;
+
+        sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+        if (sock < 0) {
+                return -errno;
+        }
+
+        if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
+                ret = -errno;
+                goto cleanup;
+        }
+
+        addrlen = sizeof(sa);
+        if (getsockname(sock, (struct sockaddr *)&sa, &addrlen) < 0) {
+                ret = -errno;
+                goto cleanup;
+        }
+
+        if (addrlen != sizeof(sa)) {
+                ret = -LIBBPF_ERRNO__INTERNAL;
+                goto cleanup;
+        }
+
+        memset(&req, 0, sizeof(req));
+        req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
+        req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+        req.nh.nlmsg_type = RTM_SETLINK;
+        req.nh.nlmsg_pid = 0;
+        req.nh.nlmsg_seq = ++seq;
+        req.ifinfo.ifi_family = AF_UNSPEC;
+        req.ifinfo.ifi_index = ifindex;
+
+        /* started nested attribute for XDP */
+        nla = (struct nlattr *)(((char *)&req)
+                                + NLMSG_ALIGN(req.nh.nlmsg_len));
+        nla->nla_type = NLA_F_NESTED | IFLA_XDP;
+        nla->nla_len = NLA_HDRLEN;
+
+        /* add XDP fd */
+        nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
+        nla_xdp->nla_type = IFLA_XDP_FD;
+        nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
+        memcpy((char *)nla_xdp + NLA_HDRLEN, &fd, sizeof(fd));
+        nla->nla_len += nla_xdp->nla_len;
+
+        /* if user passed in any flags, add those too */
+        if (flags) {
+                nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
+                nla_xdp->nla_type = IFLA_XDP_FLAGS;
+                nla_xdp->nla_len = NLA_HDRLEN + sizeof(flags);
+                memcpy((char *)nla_xdp + NLA_HDRLEN, &flags, sizeof(flags));
+                nla->nla_len += nla_xdp->nla_len;
+        }
+
+        req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);
+
+        if (send(sock, &req, req.nh.nlmsg_len, 0) < 0) {
+                ret = -errno;
+                goto cleanup;
+        }
+
+        len = recv(sock, buf, sizeof(buf), 0);
+        if (len < 0) {
+                ret = -errno;
+                goto cleanup;
+        }
+
+        for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
+             nh = NLMSG_NEXT(nh, len)) {
+                if (nh->nlmsg_pid != sa.nl_pid) {
+                        ret = -LIBBPF_ERRNO__WRNGPID;
+                        goto cleanup;
+                }
+                if (nh->nlmsg_seq != seq) {
+                        ret = -LIBBPF_ERRNO__INVSEQ;
+                        goto cleanup;
+                }
+                switch (nh->nlmsg_type) {
+                case NLMSG_ERROR:
+                        err = (struct nlmsgerr *)NLMSG_DATA(nh);
+                        if (!err->error)
+                                continue;
+                        ret = err->error;
+                        goto cleanup;
+                case NLMSG_DONE:
+                        break;
+                default:
+                        break;
+                }
+        }
+
+        ret = 0;
+
+cleanup:
+        close(sock);
+        return ret;
+}