Re: [PATCH bpf-next v4 1/3] libbpf: add function to setup XDP

[Eric Leblond]

Hello,

On Sat, 2017-12-30 at 21:41 +0100, Eric Leblond wrote:
> Most of the code is taken from set_link_xdp_fd() in bpf_load.c and
> slightly modified to be library compliant.

I've just discovered this patch is breaking the build of samples/bpf/
(nlattr not included at least and some int type problem). I'm going to
resubmit a patchset fixing this.

Sorry for the noise.

Best regards,
-- 
Eric Leblond 
Blog: https://home.regit.org/

[PATCH bpf-next v4 1/3] libbpf: add function to setup XDP

[Eric Leblond]

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 
Acked-by: Alexei Starovoitov 
---
 tools/lib/bpf/bpf.c| 126 -
 tools/lib/bpf/libbpf.c |   2 +
 tools/lib/bpf/libbpf.h |   4 ++
 3 files changed, 130 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 5128677e4117..f00fba2edeae 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -25,6 +25,16 @@
 #include 
 #include 
 #include "bpf.h"
+#include "libbpf.h"
+#include 
+#include 
+#include 
+
+#ifndef IFLA_XDP_MAX
+#define IFLA_XDP   43
+#define IFLA_XDP_FD1
+#define IFLA_XDP_FLAGS 3
+#endif
 
 /*
  * When building perf, unistd.h is overridden. __NR_bpf is
@@ -46,8 +56,6 @@
 # endif
 #endif
 
-#define min(x, y) ((x) < (y) ? (x) : (y))
-
 static inline __u64 ptr_to_u64(const void *ptr)
 {
return (__u64) (unsigned long) 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(, 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 *), sizeof(sa)) < 0) {
+   ret = -errno;
+   goto cleanup;
+   }
+
+   addrlen = sizeof(sa);
+   if (getsockname(sock, (struct sockaddr *), ) < 0) {
+   ret = -errno;
+   goto cleanup;
+   }
+
+   if (addrlen != sizeof(sa)) {
+   ret = -LIBBPF_ERRNO__INTERNAL;
+   goto cleanup;
+   }
+
+   memset(, 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 *))
+   + 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, , 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, , sizeof(flags));
+   nla->nla_len += nla_xdp->nla_len;
+   }
+
+   req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);
+
+   if (send(sock, , 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;
+}
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e9c4b7cabcf2..5fe8aaa2123e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -106,6 +106,8 @@ static const char *libbpf_strerror_table[NR_ERRNO] = {