[PATCH bpf-next 3/4] libbpf: Add function to set link XDP fd while specifying old fd

Toke Høiland-Jørgensen
2020-03-19T13:33:43Z

From: Toke Høiland-Jørgensen <toke@redhat.com>

This adds a new function to set the XDP fd while specifying the old fd to
replace, using the newly added IFLA_XDP_EXPECTED_FD netlink parameter.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
tools/lib/bpf/libbpf.h | 2 ++
tools/lib/bpf/libbpf.map | 1 +
tools/lib/bpf/netlink.c | 22 +++++++++++++++++++++-
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index d38d7a629417..b5ca4f741e28 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -445,6 +445,8 @@ struct xdp_link_info {
};

LIBBPF_API int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags);
+LIBBPF_API int bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd,
+ __u32 flags);
LIBBPF_API int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags);
LIBBPF_API int bpf_get_link_xdp_info(int ifindex, struct xdp_link_info *info,
size_t info_size, __u32 flags);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 5129283c0284..154f1d94fa63 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -244,4 +244,5 @@ LIBBPF_0.0.8 {
bpf_link__pin_path;
bpf_link__unpin;
bpf_program__set_attach_target;
+ bpf_set_link_xdp_fd_replace;
} LIBBPF_0.0.7;
diff --git a/tools/lib/bpf/netlink.c b/tools/lib/bpf/netlink.c
index 431bd25c6cdb..39bd0ead1546 100644
--- a/tools/lib/bpf/netlink.c
+++ b/tools/lib/bpf/netlink.c
@@ -132,7 +132,8 @@ static int bpf_netlink_recv(int sock, __u32 nl_pid, int seq,
return ret;
}

-int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
+static int __bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd,
+ __u32 flags)
{
int sock, seq = 0, ret;
struct nlattr *nla, *nla_xdp;
@@ -178,6 +179,14 @@ int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
nla->nla_len += nla_xdp->nla_len;
}

+ if (flags & XDP_FLAGS_EXPECT_FD) {
+ nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
+ nla_xdp->nla_type = IFLA_XDP_EXPECTED_FD;
+ nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
+ memcpy((char *)nla_xdp + NLA_HDRLEN, &old_fd, sizeof(old_fd));
+ 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) {
@@ -191,6 +200,17 @@ int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
return ret;
}

+int bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd, __u32 flags)
+{
+ return __bpf_set_link_xdp_fd_replace(ifindex, fd, old_fd,
+ flags | XDP_FLAGS_EXPECT_FD);
+}
+
+int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
+{
+ return __bpf_set_link_xdp_fd_replace(ifindex, fd, -1, flags);
+}
+
static int __dump_link_nlmsg(struct nlmsghdr *nlh,
libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
{