Commit 3b39d73c authored by Jakub Kicinski's avatar Jakub Kicinski Committed by Alexei Starovoitov
Browse files

bpftool: Fix truncated netlink dumps 



Netlink requires that the recv buffer used during dumps is at least
min(PAGE_SIZE, 8k) (see the man page). Otherwise the messages will
get truncated. Make sure bpftool follows this requirement, avoid
missing information on systems with large pages.

Acked-by: default avatarQuentin Monnet <qmo@kernel.org>
Fixes: 7084566a ("tools/bpftool: Remove libbpf_internal.h usage in bpftool")
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20260217194150.734701-1-kuba@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 593fffb8

tools/bpf/bpftool/net.c

+4 −1
Original line number Diff line number Diff line
@@ -156,7 +156,7 @@ static int netlink_recv(int sock, __u32 nl_pid, __u32 seq, 
	bool multipart = true;

	struct nlmsgerr *err;

	struct nlmsghdr *nh;

	char buf[4096];

	char buf[8192];

	int len, ret;



	while (multipart) {
@@ -201,6 +201,9 @@ static int netlink_recv(int sock, __u32 nl_pid, __u32 seq, 
					return ret;

			}

		}



		if (len)

			p_err("Invalid message or trailing data in Netlink response: %d bytes left", len);

	}

	ret = 0;

done:

tools/lib/bpf/netlink.c

+3 −1
Original line number Diff line number Diff line
@@ -143,7 +143,7 @@ static int libbpf_netlink_recv(int sock, __u32 nl_pid, int seq, 
	struct nlmsghdr *nh;

	int len, ret;



	ret = alloc_iov(&iov, 4096);

	ret = alloc_iov(&iov, 8192);

	if (ret)

		goto done;
@@ -212,6 +212,8 @@ static int libbpf_netlink_recv(int sock, __u32 nl_pid, int seq, 
				}

			}

		}

		if (len)

			pr_warn("Invalid message or trailing data in Netlink response: %d bytes left\n", len);

	}

	ret = 0;

done: