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

Message ID 158462359530.164779.12468969809718921559.stgit@toke.dk
State New
Headers show
Series [bpf-next,1/4] xdp: Support specifying expected existing program when attaching XDP | expand

Commit Message

Toke Høiland-Jørgensen March 19, 2020, 1:13 p.m. UTC 
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(-)
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Patch

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)
 {