netlink: fix compatibility with older netlink applications.
Some apps try to provide only the non-zero part of the required message header instead of the full one. It happens when fetching routes or interface addresses, where the first header byte is the family. This behavior is "illegal" under the "strict" Netlink socket option, however there are many applications out there doing things in the "old" way. Support this usecase by copying the provided bytes into the temporary zero-filled header and running the parser on this header instead. Reported by: Goran Mekić <meka@tilda.center>
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@ -213,9 +213,19 @@ nl_parse_header(void *hdr, int len, const struct nlhdr_parser *parser,
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int error;
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if (__predict_false(len < parser->nl_hdr_off)) {
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nlmsg_report_err_msg(npt, "header too short: expected %d, got %d",
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parser->nl_hdr_off, len);
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return (EINVAL);
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if (npt->strict) {
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nlmsg_report_err_msg(npt, "header too short: expected %d, got %d",
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parser->nl_hdr_off, len);
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return (EINVAL);
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}
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/* Compat with older applications: pretend there's a full header */
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void *tmp_hdr = npt_alloc(npt, parser->nl_hdr_off);
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if (tmp_hdr == NULL)
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return (EINVAL);
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memcpy(tmp_hdr, hdr, len);
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hdr = tmp_hdr;
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len = parser->nl_hdr_off;
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}
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if (npt->strict && parser->sp != NULL && !parser->sp(hdr, npt))
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@ -8,6 +8,7 @@
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from atf_python.sys.net.netlink import NlConst
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from atf_python.sys.net.netlink import NlHelper
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from atf_python.sys.net.netlink import NlmBaseFlags
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from atf_python.sys.net.netlink import Nlmsghdr
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from atf_python.sys.net.netlink import NlMsgType
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from atf_python.sys.net.netlink import NlRtMsgType
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from atf_python.sys.net.netlink import Nlsock
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@ -68,6 +69,25 @@ def test_46_filter_iface(self):
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assert len([r for r in ret if r[0] == ifname and r[1] == socket.AF_INET6]) == 2
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assert len(ret) == 3
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def test_46_filter_family_compat(self):
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"""Tests that family filtering works with the stripped header"""
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hdr = Nlmsghdr(
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nlmsg_len=17,
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nlmsg_type=NlRtMsgType.RTM_GETADDR.value,
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nlmsg_flags=NlmBaseFlags.NLM_F_ACK.value | NlmBaseFlags.NLM_F_REQUEST.value,
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nlmsg_seq=self.helper.get_seq()
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)
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data = bytes(hdr) + struct.pack("@B", socket.AF_INET)
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self.nlsock.write_data(data)
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ret = []
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for rx_msg in self.read_msg_list(hdr.nlmsg_seq, NlRtMsgType.RTM_NEWADDR):
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ifname = socket.if_indextoname(rx_msg.base_hdr.ifa_index)
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family = rx_msg.base_hdr.ifa_family
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ret.append((ifname, family, rx_msg))
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assert len(ret) == 2
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def filter_iface_family(self, family, num_items):
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"""Tests that listing outputs IPv4 for the specific interface"""
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epair_ifname = self.vnet.iface_alias_map["if1"].name
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