Re: [PATCH net-next 3/3] selftests/net: fix GRO coalesce test and add ext

From: Willem de Bruijn
Date: Tue Dec 26 2023 - 16:16:30 EST

Richard Gobert wrote:
> Currently there is no test which checks that IPv6 extension header packets
> successfully coalesce. This commit adds a test, which verifies two IPv6
> packets with HBH extension headers do coalesce.
>
> I changed the receive socket filter to accept a packet with one extension
> header. This change exposed a bug in the fragment test -- the old BPF did
> not accept the fragment packet. I updated correct_num_packets in the
> fragment test accordingly.
>
> Signed-off-by: Richard Gobert <richardbgobert@xxxxxxxxx>

Thanks for adding test coverage along with the feature, and as part
of the existing gro test too.

> ---
> tools/testing/selftests/net/gro.c | 78 ++++++++++++++++++++++++++++---
> 1 file changed, 71 insertions(+), 7 deletions(-)
>
> diff --git a/tools/testing/selftests/net/gro.c b/tools/testing/selftests/net/gro.c
> index 30024d0ed373..4ee34dca8e5f 100644
> --- a/tools/testing/selftests/net/gro.c
> +++ b/tools/testing/selftests/net/gro.c
> @@ -71,6 +71,10 @@
> #define MAX_PAYLOAD (IP_MAXPACKET - sizeof(struct tcphdr) - sizeof(struct ipv6hdr))
> #define NUM_LARGE_PKT (MAX_PAYLOAD / MSS)
> #define MAX_HDR_LEN (ETH_HLEN + sizeof(struct ipv6hdr) + sizeof(struct tcphdr))
> +#define MIN_EXTHDR_SIZE 8 /* minimum size of IPv6 extension header */
> +
> +#define ipv6_optlen(p) (((p)->hdrlen+1) << 3) /* calculate IPv6 extension header len */
> +
>
> static const char *addr6_src = "fdaa::2";
> static const char *addr6_dst = "fdaa::1";
> @@ -104,7 +108,7 @@ static void setup_sock_filter(int fd)
> const int dport_off = tcp_offset + offsetof(struct tcphdr, dest);
> const int ethproto_off = offsetof(struct ethhdr, h_proto);
> int optlen = 0;
> - int ipproto_off;
> + int ipproto_off, opt_ipproto_off;
> int next_off;
>
> if (proto == PF_INET)
> @@ -116,14 +120,27 @@ static void setup_sock_filter(int fd)
> if (strcmp(testname, "ip") == 0) {
> if (proto == PF_INET)
> optlen = sizeof(struct ip_timestamp);
> - else
> - optlen = sizeof(struct ip6_frag);
> + else {
> + // same size for HBH and Fragment extension header types

no C++ style comments

Also, instead of comments here and at the MIN_EXTHDR_SIZE definition,
perhaps cleaner as self documenting code:

BUILD_BUG_ON(MIN_EXTHDR_SIZE != sizeof(struct ip6_hbh));
BUILD_BUG_ON(MIN_EXTHDR_SIZE != sizeof(struct ip6_dest));
BUILD_BUG_ON(MIN_EXTHDR_SIZE < sizeof(struct ip6_frag));

> + optlen = MIN_EXTHDR_SIZE;
> + opt_ipproto_off = ETH_HLEN + sizeof(struct ipv6hdr) +
> + offsetof(struct ip6_ext, ip6e_nxt);
> + }
> }
>
> + /*
> + * this filter validates the following:
> + * - packet is IPv4/IPv6 according to the running test.
> + * - packet is TCP. Also handles the case of one extension header and then TCP.
> + * - checks the packet tcp dport equals to DPORT.
> + * (also handles the case of one extension header and then TCP.)
> + */

nit: for filewide consistency: netdev style:

/* start comment
* more comment
*/

> struct sock_filter filter[] = {
> BPF_STMT(BPF_LD + BPF_H + BPF_ABS, ethproto_off),
> - BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ntohs(ethhdr_proto), 0, 7),
> + BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ntohs(ethhdr_proto), 0, 9),
> BPF_STMT(BPF_LD + BPF_B + BPF_ABS, ipproto_off),
> + BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_TCP, 2, 0),
> + BPF_STMT(BPF_LD + BPF_B + BPF_ABS, opt_ipproto_off),
> BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_TCP, 0, 5),
> BPF_STMT(BPF_LD + BPF_H + BPF_ABS, dport_off),
> BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DPORT, 2, 0),
> @@ -576,6 +593,39 @@ static void add_ipv4_ts_option(void *buf, void *optpkt)
> iph->check = checksum_fold(iph, sizeof(struct iphdr) + optlen, 0);
> }
>
> +static void add_ipv6_exthdr(void *buf, void *optpkt, __u8 exthdr_type)
> +{
> + struct ipv6_opt_hdr *hbh_hdr = (struct ipv6_opt_hdr *)(optpkt + tcp_offset);
> + struct ipv6hdr *iph = (struct ipv6hdr *)(optpkt + ETH_HLEN);
> + int opt_len;
> +
> + hbh_hdr->hdrlen = 0;
> + hbh_hdr->nexthdr = IPPROTO_TCP;
> + opt_len = ipv6_optlen(hbh_hdr);
> +
> + memcpy(optpkt, buf, tcp_offset);
> + memcpy(optpkt + tcp_offset + MIN_EXTHDR_SIZE, buf + tcp_offset,
> + sizeof(struct tcphdr) + PAYLOAD_LEN);
> +
> + iph->nexthdr = exthdr_type;
> + iph->payload_len = htons(ntohs(iph->payload_len) + MIN_EXTHDR_SIZE);
> +}
> +
> +/* Send IPv6 packet with extension header */
> +static void send_ipv6_exthdr(int fd, struct sockaddr_ll *daddr)
> +{
> + static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
> + static char exthdr_pck[sizeof(buf) + MIN_EXTHDR_SIZE];
> +
> + create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
> + add_ipv6_exthdr(buf, exthdr_pck, IPPROTO_HOPOPTS);
> + write_packet(fd, exthdr_pck, total_hdr_len + PAYLOAD_LEN + MIN_EXTHDR_SIZE, daddr);
> +
> + create_packet(buf, PAYLOAD_LEN * 1, 0, PAYLOAD_LEN, 0);
> + add_ipv6_exthdr(buf, exthdr_pck, IPPROTO_HOPOPTS);
> + write_packet(fd, exthdr_pck, total_hdr_len + PAYLOAD_LEN + MIN_EXTHDR_SIZE, daddr);
> +}
> +
> /* IPv4 options shouldn't coalesce */
> static void send_ip_options(int fd, struct sockaddr_ll *daddr)
> {
> @@ -697,7 +747,7 @@ static void send_fragment6(int fd, struct sockaddr_ll *daddr)
> create_packet(buf, PAYLOAD_LEN * i, 0, PAYLOAD_LEN, 0);
> write_packet(fd, buf, bufpkt_len, daddr);
> }
> -
> + sleep(1);

Leftover debug, or necessary fix to existing test?
> create_packet(buf, PAYLOAD_LEN * 2, 0, PAYLOAD_LEN, 0);
> memset(extpkt, 0, extpkt_len);
>
> @@ -760,6 +810,7 @@ static void check_recv_pkts(int fd, int *correct_payload,
> vlog("}, Total %d packets\nReceived {", correct_num_pkts);
>
> while (1) {
> + ip_ext_len = 0;
> pkt_size = recv(fd, buffer, IP_MAXPACKET + ETH_HLEN + 1, 0);
> if (pkt_size < 0)
> error(1, errno, "could not receive");
> @@ -767,7 +818,7 @@ static void check_recv_pkts(int fd, int *correct_payload,
> if (iph->version == 4)
> ip_ext_len = (iph->ihl - 5) * 4;
> else if (ip6h->version == 6 && ip6h->nexthdr != IPPROTO_TCP)
> - ip_ext_len = sizeof(struct ip6_frag);
> + ip_ext_len = MIN_EXTHDR_SIZE;

struct ip6_frag is > MIN_EXTHDR_SIZE. Need both cases?

else if (ip6h->version == 6 && ip6h->nexthdr == NEXTHDR_FRAGMENT
ip_ext_len = sizeof(struct ip6_frag);
else if (ip6h->version == 6 && ip6h->nexthdr != IPPROTO_TCP)
ip_ext_len = MIN_EXTHDR_SIZE;

>
> tcph = (struct tcphdr *)(buffer + tcp_offset + ip_ext_len);
>
> @@ -880,7 +931,14 @@ static void gro_sender(void)
> sleep(1);
> write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
> } else if (proto == PF_INET6) {
> + sleep(1);
> send_fragment6(txfd, &daddr);
> + sleep(1);
> + write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
> +
> + sleep(1);
> + send_ipv6_exthdr(txfd, &daddr);
> + sleep(1);

For the casual reader: these sleeps are not leftover debug statements
unfortunately. The same exists in the PF_INET branch:

/* Modified packets may be received out of order.
* Sleep function added to enforce test boundaries
* so that fin pkts are not received prior to other pkts.
*/

> write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
> }
> } else if (strcmp(testname, "large") == 0) {
> @@ -997,7 +1055,13 @@ static void gro_receiver(void)
> */
> printf("fragmented ip6 doesn't coalesce: ");
> correct_payload[0] = PAYLOAD_LEN * 2;
> - check_recv_pkts(rxfd, correct_payload, 2);
> + correct_payload[1] = PAYLOAD_LEN;
> + correct_payload[2] = PAYLOAD_LEN;
> + check_recv_pkts(rxfd, correct_payload, 3);
> +
> + correct_payload[0] = PAYLOAD_LEN * 2;
> + printf("ipv6 with extension header DOES coalesce: ");
> + check_recv_pkts(rxfd, correct_payload, 1);

It might be worth adding a test with two different extension headers.
To verify that these should not coalesce.

Either different ipprotos, like IPPROTO_DSTOPTS vs IPPROTO_HOPOPTS.
Perhaps more intesting are two of the same ipproto but with different
content.

> }
> } else if (strcmp(testname, "large") == 0) {
> int offset = proto == PF_INET ? 20 : 0;
> --
> 2.36.1
>