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Date: Wed, 24 Jul 2019 22:36:23 -0700
From: Song Liu <liu.song.a23@...il.com>
To: Stanislav Fomichev <sdf@...ichev.me>
Cc: Stanislav Fomichev <sdf@...gle.com>,
Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
"David S . Miller" <davem@...emloft.net>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Willem de Bruijn <willemb@...gle.com>,
Petar Penkov <ppenkov@...gle.com>
Subject: Re: [PATCH bpf-next 5/7] sefltests/bpf: support FLOW_DISSECTOR_F_PARSE_1ST_FRAG
On Wed, Jul 24, 2019 at 4:52 PM Stanislav Fomichev <sdf@...ichev.me> wrote:
>
> On 07/24, Song Liu wrote:
> > On Wed, Jul 24, 2019 at 10:11 AM Stanislav Fomichev <sdf@...gle.com> wrote:
> > >
> > > bpf_flow.c: exit early unless FLOW_DISSECTOR_F_PARSE_1ST_FRAG is passed
> > > in flags. Also, set ip_proto earlier, this makes sure we have correct
> > > value with fragmented packets.
> > >
> > > Add selftest cases to test ipv4/ipv6 fragments and skip eth_get_headlen
> > > tests that don't have FLOW_DISSECTOR_F_PARSE_1ST_FRAG flag.
> > >
> > > eth_get_headlen calls flow dissector with
> > > FLOW_DISSECTOR_F_PARSE_1ST_FRAG flag so we can't run tests that
> > > have different set of input flags against it.
> > >
> > > Cc: Willem de Bruijn <willemb@...gle.com>
> > > Cc: Petar Penkov <ppenkov@...gle.com>
> > > Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> > > ---
> > > .../selftests/bpf/prog_tests/flow_dissector.c | 129 ++++++++++++++++++
> > > tools/testing/selftests/bpf/progs/bpf_flow.c | 28 +++-
> > > 2 files changed, 151 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/bpf/prog_tests/flow_dissector.c b/tools/testing/selftests/bpf/prog_tests/flow_dissector.c
> > > index c938283ac232..966cb3b06870 100644
> > > --- a/tools/testing/selftests/bpf/prog_tests/flow_dissector.c
> > > +++ b/tools/testing/selftests/bpf/prog_tests/flow_dissector.c
> > > @@ -5,6 +5,10 @@
> > > #include <linux/if_tun.h>
> > > #include <sys/uio.h>
> > >
> > > +#ifndef IP_MF
> > > +#define IP_MF 0x2000
> > > +#endif
> > > +
> > > #define CHECK_FLOW_KEYS(desc, got, expected) \
> > > CHECK_ATTR(memcmp(&got, &expected, sizeof(got)) != 0, \
> > > desc, \
> > > @@ -49,6 +53,18 @@ struct ipv6_pkt {
> > > struct tcphdr tcp;
> > > } __packed;
> > >
> > > +struct ipv6_frag_pkt {
> > > + struct ethhdr eth;
> > > + struct ipv6hdr iph;
> > > + struct frag_hdr {
> > > + __u8 nexthdr;
> > > + __u8 reserved;
> > > + __be16 frag_off;
> > > + __be32 identification;
> > > + } ipf;
> > > + struct tcphdr tcp;
> > > +} __packed;
> > > +
> > > struct dvlan_ipv6_pkt {
> > > struct ethhdr eth;
> > > __u16 vlan_tci;
> > > @@ -65,9 +81,11 @@ struct test {
> > > struct ipv4_pkt ipv4;
> > > struct svlan_ipv4_pkt svlan_ipv4;
> > > struct ipv6_pkt ipv6;
> > > + struct ipv6_frag_pkt ipv6_frag;
> > > struct dvlan_ipv6_pkt dvlan_ipv6;
> > > } pkt;
> > > struct bpf_flow_keys keys;
> > > + __u32 flags;
> > > };
> > >
> > > #define VLAN_HLEN 4
> > > @@ -143,6 +161,102 @@ struct test tests[] = {
> > > .n_proto = __bpf_constant_htons(ETH_P_IPV6),
> > > },
> > > },
> > > + {
> > > + .name = "ipv4-frag",
> > > + .pkt.ipv4 = {
> > > + .eth.h_proto = __bpf_constant_htons(ETH_P_IP),
> > > + .iph.ihl = 5,
> > > + .iph.protocol = IPPROTO_TCP,
> > > + .iph.tot_len = __bpf_constant_htons(MAGIC_BYTES),
> > > + .iph.frag_off = __bpf_constant_htons(IP_MF),
> > > + .tcp.doff = 5,
> > > + .tcp.source = 80,
> > > + .tcp.dest = 8080,
> > > + },
> > > + .keys = {
> > > + .flags = FLOW_DISSECTOR_F_PARSE_1ST_FRAG,
> > > + .nhoff = ETH_HLEN,
> > > + .thoff = ETH_HLEN + sizeof(struct iphdr),
> > > + .addr_proto = ETH_P_IP,
> > > + .ip_proto = IPPROTO_TCP,
> > > + .n_proto = __bpf_constant_htons(ETH_P_IP),
> > > + .is_frag = true,
> > > + .is_first_frag = true,
> > > + .sport = 80,
> > > + .dport = 8080,
> > > + },
> > > + .flags = FLOW_DISSECTOR_F_PARSE_1ST_FRAG,
> > > + },
> > > + {
> > > + .name = "ipv4-no-frag",
> > > + .pkt.ipv4 = {
> > > + .eth.h_proto = __bpf_constant_htons(ETH_P_IP),
> > > + .iph.ihl = 5,
> > > + .iph.protocol = IPPROTO_TCP,
> > > + .iph.tot_len = __bpf_constant_htons(MAGIC_BYTES),
> > > + .iph.frag_off = __bpf_constant_htons(IP_MF),
> > > + .tcp.doff = 5,
> > > + .tcp.source = 80,
> > > + .tcp.dest = 8080,
> > > + },
> > > + .keys = {
> > > + .nhoff = ETH_HLEN,
> > > + .thoff = ETH_HLEN + sizeof(struct iphdr),
> > > + .addr_proto = ETH_P_IP,
> > > + .ip_proto = IPPROTO_TCP,
> > > + .n_proto = __bpf_constant_htons(ETH_P_IP),
> > > + .is_frag = true,
> > > + .is_first_frag = true,
> > > + },
> > > + },
> > > + {
> > > + .name = "ipv6-frag",
> > > + .pkt.ipv6_frag = {
> > > + .eth.h_proto = __bpf_constant_htons(ETH_P_IPV6),
> > > + .iph.nexthdr = IPPROTO_FRAGMENT,
> > > + .iph.payload_len = __bpf_constant_htons(MAGIC_BYTES),
> > > + .ipf.nexthdr = IPPROTO_TCP,
> > > + .tcp.doff = 5,
> > > + .tcp.source = 80,
> > > + .tcp.dest = 8080,
> > > + },
> > > + .keys = {
> > > + .flags = FLOW_DISSECTOR_F_PARSE_1ST_FRAG,
> > > + .nhoff = ETH_HLEN,
> > > + .thoff = ETH_HLEN + sizeof(struct ipv6hdr) +
> > > + sizeof(struct frag_hdr),
> > > + .addr_proto = ETH_P_IPV6,
> > > + .ip_proto = IPPROTO_TCP,
> > > + .n_proto = __bpf_constant_htons(ETH_P_IPV6),
> > > + .is_frag = true,
> > > + .is_first_frag = true,
> > > + .sport = 80,
> > > + .dport = 8080,
> > > + },
> > > + .flags = FLOW_DISSECTOR_F_PARSE_1ST_FRAG,
> > > + },
> > > + {
> > > + .name = "ipv6-no-frag",
> > > + .pkt.ipv6_frag = {
> > > + .eth.h_proto = __bpf_constant_htons(ETH_P_IPV6),
> > > + .iph.nexthdr = IPPROTO_FRAGMENT,
> > > + .iph.payload_len = __bpf_constant_htons(MAGIC_BYTES),
> > > + .ipf.nexthdr = IPPROTO_TCP,
> > > + .tcp.doff = 5,
> > > + .tcp.source = 80,
> > > + .tcp.dest = 8080,
> > > + },
> > > + .keys = {
> > > + .nhoff = ETH_HLEN,
> > > + .thoff = ETH_HLEN + sizeof(struct ipv6hdr) +
> > > + sizeof(struct frag_hdr),
> > > + .addr_proto = ETH_P_IPV6,
> > > + .ip_proto = IPPROTO_TCP,
> > > + .n_proto = __bpf_constant_htons(ETH_P_IPV6),
> > > + .is_frag = true,
> > > + .is_first_frag = true,
> > > + },
> > > + },
> > > };
> > >
> > > static int create_tap(const char *ifname)
> > > @@ -225,6 +339,13 @@ void test_flow_dissector(void)
> > > .data_size_in = sizeof(tests[i].pkt),
> > > .data_out = &flow_keys,
> > > };
> > > + static struct bpf_flow_keys ctx = {};
> > > +
> > > + if (tests[i].flags) {
> > > + tattr.ctx_in = &ctx;
> > > + tattr.ctx_size_in = sizeof(ctx);
> > > + ctx.flags = tests[i].flags;
> > > + }
> > >
> > > err = bpf_prog_test_run_xattr(&tattr);
> > > CHECK_ATTR(tattr.data_size_out != sizeof(flow_keys) ||
> > > @@ -255,6 +376,14 @@ void test_flow_dissector(void)
> > > struct bpf_prog_test_run_attr tattr = {};
> > > __u32 key = 0;
> > >
> > > + /* Don't run tests that are not marked as
> > > + * FLOW_DISSECTOR_F_PARSE_1ST_FRAG; eth_get_headlen
> > > + * sets this flag.
> > > + */
> > > +
> > > + if (tests[i].flags != FLOW_DISSECTOR_F_PARSE_1ST_FRAG)
> > > + continue;
> >
> > Maybe test flags & FLOW_DISSECTOR_F_PARSE_1ST_FRAG == 0 instead?
> > It is not necessary now, but might be useful in the future.
> I'm not sure about this one. We want flags here to match flags
> from eth_get_headlen:
>
> const unsigned int flags = FLOW_DISSECTOR_F_PARSE_1ST_FRAG;
> ...
> if (!skb_flow_dissect_flow_keys_basic(..., flags))
>
> Otherwise the test might break unexpectedly. So I'd rather manually
> adjust a test here if eth_get_headlen flags change.
Could we have
flags == FLOW_DISSECTOR_F_PARSE_1ST_FRAG | some_other_flag
in the future? This flag is not equal to FLOW_DISSECTOR_F_PARSE_1ST_FRAG.
>
> Maybe I should clarify the comment to signify that dependency? Because
> currently it might be read as if we only care about
> FLOW_DISSECTOR_F_PARSE_1ST_FRAG, but we really care about all flags
> in eth_get_headlen; it just happens that it only has one right now.
Some clarification will be great.
Thanks,
Song
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