Subject: Re: [PATCH RFC net-next v2 2/6] selftests: ncdevmem: Implement devmem TCP TX

From: Stanislav Fomichev <[email-masked]>
Date: Fri, 31 Jan 2025 09:41:50 -0800

On 01/30, Mina Almasry wrote:
> On Thu, Jan 30, 2025 at 3:05 PM Stanislav Fomichev <[email-masked]> wrote:
> >
> > On 01/30, Mina Almasry wrote:
> > > Add support for devmem TX in ncdevmem.
> > >
> > > This is a combination of the ncdevmem from the devmem TCP series RFCv1
> > > which included the TX path, and work by Stan to include the netlink API
> > > and refactored on top of his generic memory_provider support.
> > >
> > > Signed-off-by: Mina Almasry <[email-masked]>
> > > Signed-off-by: Stanislav Fomichev <[email-masked]>
> > >
> > > ---
> > >
> > > v2:
> > > - make errors a static variable so that we catch instances where there
> > >   are less than 20 errors across different buffers.
> > > - Fix the issue where the seed is reset to 0 instead of its starting
> > >   value 1.
> > > - Use 1000ULL instead of 1000 to guard against overflow (Willem).
> > > - Do not set POLLERR (Willem).
> > > - Update the test to use the new interface where iov_base is the
> > >   dmabuf_offset.
> > > - Update the test to send 2 iov instead of 1, so we get some test
> > >   coverage over sending multiple iovs at once.
> > > - Print the ifindex the test is using, useful for debugging issues where
> > >   maybe the test may fail because the ifindex of the socket is different
> > >   from the dmabuf binding.
> > > ---
> > >  .../selftests/drivers/net/hw/ncdevmem.c       | 276 +++++++++++++++++-
> > >  1 file changed, 272 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/drivers/net/hw/ncdevmem.c b/tools/testing/selftests/drivers/net/hw/ncdevmem.c
> > > index 19a6969643f4..8455f19ecd1a 100644
> > > --- a/tools/testing/selftests/drivers/net/hw/ncdevmem.c
> > > +++ b/tools/testing/selftests/drivers/net/hw/ncdevmem.c
> > > @@ -40,15 +40,18 @@
> > >  #include <fcntl.h>
> > >  #include <malloc.h>
> > >  #include <error.h>
> > > +#include <poll.h>
> > >
> > >  #include <arpa/inet.h>
> > >  #include <sys/socket.h>
> > >  #include <sys/mman.h>
> > >  #include <sys/ioctl.h>
> > >  #include <sys/syscall.h>
> > > +#include <sys/time.h>
> > >
> > >  #include <linux/memfd.h>
> > >  #include <linux/dma-buf.h>
> > > +#include <linux/errqueue.h>
> > >  #include <linux/udmabuf.h>
> > >  #include <libmnl/libmnl.h>
> > >  #include <linux/types.h>
> > > @@ -80,6 +83,8 @@ static int num_queues = -1;
> > >  static char *ifname;
> > >  static unsigned int ifindex;
> > >  static unsigned int dmabuf_id;
> > > +static uint32_t tx_dmabuf_id;
> > > +static int waittime_ms = 500;
> > >
> > >  struct memory_buffer {
> > >       int fd;
> > > @@ -93,6 +98,8 @@ struct memory_buffer {
> > >  struct memory_provider {
> > >       struct memory_buffer *(*alloc)(size_t size);
> > >       void (*free)(struct memory_buffer *ctx);
> > > +     void (*memcpy_to_device)(struct memory_buffer *dst, size_t off,
> > > +                              void *src, int n);
> > >       void (*memcpy_from_device)(void *dst, struct memory_buffer *src,
> > >                                  size_t off, int n);
> > >  };
> > > @@ -153,6 +160,20 @@ static void udmabuf_free(struct memory_buffer *ctx)
> > >       free(ctx);
> > >  }
> > >
> > > +static void udmabuf_memcpy_to_device(struct memory_buffer *dst, size_t off,
> > > +                                  void *src, int n)
> > > +{
> > > +     struct dma_buf_sync sync = {};
> > > +
> > > +     sync.flags = DMA_BUF_SYNC_START | DMA_BUF_SYNC_WRITE;
> > > +     ioctl(dst->fd, DMA_BUF_IOCTL_SYNC, &sync);
> > > +
> > > +     memcpy(dst->buf_mem + off, src, n);
> > > +
> > > +     sync.flags = DMA_BUF_SYNC_END | DMA_BUF_SYNC_WRITE;
> > > +     ioctl(dst->fd, DMA_BUF_IOCTL_SYNC, &sync);
> > > +}
> > > +
> > >  static void udmabuf_memcpy_from_device(void *dst, struct memory_buffer *src,
> > >                                      size_t off, int n)
> > >  {
> > > @@ -170,6 +191,7 @@ static void udmabuf_memcpy_from_device(void *dst, struct memory_buffer *src,
> > >  static struct memory_provider udmabuf_memory_provider = {
> > >       .alloc = udmabuf_alloc,
> > >       .free = udmabuf_free,
> > > +     .memcpy_to_device = udmabuf_memcpy_to_device,
> > >       .memcpy_from_device = udmabuf_memcpy_from_device,
> > >  };
> > >
> > > @@ -188,7 +210,7 @@ void validate_buffer(void *line, size_t size)
> > >  {
> > >       static unsigned char seed = 1;
> > >       unsigned char *ptr = line;
> > > -     int errors = 0;
> > > +     static int errors;
> > >       size_t i;
> > >
> > >       for (i = 0; i < size; i++) {
> > > @@ -202,7 +224,7 @@ void validate_buffer(void *line, size_t size)
> > >               }
> > >               seed++;
> > >               if (seed == do_validation)
> > > -                     seed = 0;
> > > +                     seed = 1;
> > >       }
> > >
> > >       fprintf(stdout, "Validated buffer\n");
> > > @@ -394,6 +416,49 @@ static int bind_rx_queue(unsigned int ifindex, unsigned int dmabuf_fd,
> > >       return -1;
> > >  }
> > >
> > > +static int bind_tx_queue(unsigned int ifindex, unsigned int dmabuf_fd,
> > > +                      struct ynl_sock **ys)
> > > +{
> > > +     struct netdev_bind_tx_req *req = NULL;
> > > +     struct netdev_bind_tx_rsp *rsp = NULL;
> > > +     struct ynl_error yerr;
> > > +
> > > +     *ys = ynl_sock_create(&ynl_netdev_family, &yerr);
> > > +     if (!*ys) {
> > > +             fprintf(stderr, "YNL: %s\n", yerr.msg);
> > > +             return -1;
> > > +     }
> > > +
> > > +     req = netdev_bind_tx_req_alloc();
> > > +     netdev_bind_tx_req_set_ifindex(req, ifindex);
> > > +     netdev_bind_tx_req_set_fd(req, dmabuf_fd);
> > > +
> > > +     rsp = netdev_bind_tx(*ys, req);
> > > +     if (!rsp) {
> > > +             perror("netdev_bind_tx");
> > > +             goto err_close;
> > > +     }
> > > +
> > > +     if (!rsp->_present.id) {
> > > +             perror("id not present");
> > > +             goto err_close;
> > > +     }
> > > +
> > > +     fprintf(stderr, "got tx dmabuf id=%d\n", rsp->id);
> > > +     tx_dmabuf_id = rsp->id;
> > > +
> > > +     netdev_bind_tx_req_free(req);
> > > +     netdev_bind_tx_rsp_free(rsp);
> > > +
> > > +     return 0;
> > > +
> > > +err_close:
> > > +     fprintf(stderr, "YNL failed: %s\n", (*ys)->err.msg);
> > > +     netdev_bind_tx_req_free(req);
> > > +     ynl_sock_destroy(*ys);
> > > +     return -1;
> > > +}
> > > +
> > >  static void enable_reuseaddr(int fd)
> > >  {
> > >       int opt = 1;
> > > @@ -432,7 +497,7 @@ static int parse_address(const char *str, int port, struct sockaddr_in6 *sin6)
> > >       return 0;
> > >  }
> > >
> > > -int do_server(struct memory_buffer *mem)
> > > +static int do_server(struct memory_buffer *mem)
> > >  {
> > >       char ctrl_data[sizeof(int) * 20000];
> > >       struct netdev_queue_id *queues;
> > > @@ -686,6 +751,207 @@ void run_devmem_tests(void)
> > >       provider->free(mem);
> > >  }
> > >
> > > +static uint64_t gettimeofday_ms(void)
> > > +{
> > > +     struct timeval tv;
> > > +
> > > +     gettimeofday(&tv, NULL);
> > > +     return (tv.tv_sec * 1000ULL) + (tv.tv_usec / 1000ULL);
> > > +}
> > > +
> > > +static int do_poll(int fd)
> > > +{
> > > +     struct pollfd pfd;
> > > +     int ret;
> > > +
> > > +     pfd.revents = 0;
> > > +     pfd.fd = fd;
> > > +
> > > +     ret = poll(&pfd, 1, waittime_ms);
> > > +     if (ret == -1)
> > > +             error(1, errno, "poll");
> > > +
> > > +     return ret && (pfd.revents & POLLERR);
> > > +}
> > > +
> > > +static void wait_compl(int fd)
> > > +{
> > > +     int64_t tstop = gettimeofday_ms() + waittime_ms;
> > > +     char control[CMSG_SPACE(100)] = {};
> > > +     struct sock_extended_err *serr;
> > > +     struct msghdr msg = {};
> > > +     struct cmsghdr *cm;
> > > +     int retries = 10;
> > > +     __u32 hi, lo;
> > > +     int ret;
> > > +
> > > +     msg.msg_control = control;
> > > +     msg.msg_controllen = sizeof(control);
> > > +
> > > +     while (gettimeofday_ms() < tstop) {
> > > +             if (!do_poll(fd))
> > > +                     continue;
> > > +
> > > +             ret = recvmsg(fd, &msg, MSG_ERRQUEUE);
> > > +             if (ret < 0) {
> > > +                     if (errno == EAGAIN)
> > > +                             continue;
> > > +                     error(1, ret, "recvmsg(MSG_ERRQUEUE)");
> > > +                     return;
> > > +             }
> > > +             if (msg.msg_flags & MSG_CTRUNC)
> > > +                     error(1, 0, "MSG_CTRUNC\n");
> > > +
> > > +             for (cm = CMSG_FIRSTHDR(&msg); cm; cm = CMSG_NXTHDR(&msg, cm)) {
> > > +                     if (cm->cmsg_level != SOL_IP &&
> > > +                         cm->cmsg_level != SOL_IPV6)
> > > +                             continue;
> > > +                     if (cm->cmsg_level == SOL_IP &&
> > > +                         cm->cmsg_type != IP_RECVERR)
> > > +                             continue;
> > > +                     if (cm->cmsg_level == SOL_IPV6 &&
> > > +                         cm->cmsg_type != IPV6_RECVERR)
> > > +                             continue;
> > > +
> > > +                     serr = (void *)CMSG_DATA(cm);
> > > +                     if (serr->ee_origin != SO_EE_ORIGIN_ZEROCOPY)
> > > +                             error(1, 0, "wrong origin %u", serr->ee_origin);
> > > +                     if (serr->ee_errno != 0)
> > > +                             error(1, 0, "wrong errno %d", serr->ee_errno);
> > > +
> > > +                     hi = serr->ee_data;
> > > +                     lo = serr->ee_info;
> > > +
> > > +                     fprintf(stderr, "tx complete [%d,%d]\n", lo, hi);
> > > +                     return;
> > > +             }
> > > +     }
> > > +
> > > +     error(1, 0, "did not receive tx completion");
> > > +}
> > > +
> > > +static int do_client(struct memory_buffer *mem)
> > > +{
> > > +     char ctrl_data[CMSG_SPACE(sizeof(struct dmabuf_tx_cmsg))];
> > > +     struct sockaddr_in6 server_sin;
> > > +     struct sockaddr_in6 client_sin;
> > > +     struct dmabuf_tx_cmsg ddmabuf;
> > > +     struct ynl_sock *ys = NULL;
> > > +     struct msghdr msg = {};
> > > +     ssize_t line_size = 0;
> > > +     struct cmsghdr *cmsg;
> > > +     struct iovec iov[2];
> > > +     uint64_t off = 100;
> > > +     char *line = NULL;
> > > +     size_t len = 0;
> > > +     int socket_fd;
> > > +     int ret, mid;
> > > +     int opt = 1;
> > > +
> > > +     ret = parse_address(server_ip, atoi(port), &server_sin);
> > > +     if (ret < 0)
> > > +             error(1, 0, "parse server address");
> > > +
> > > +     socket_fd = socket(AF_INET6, SOCK_STREAM, 0);
> > > +     if (socket_fd < 0)
> > > +             error(1, socket_fd, "create socket");
> > > +
> > > +     enable_reuseaddr(socket_fd);
> > > +
> > > +     ret = setsockopt(socket_fd, SOL_SOCKET, SO_BINDTODEVICE, ifname,
> > > +                      strlen(ifname) + 1);
> > > +     if (ret)
> > > +             error(1, ret, "bindtodevice");
> > > +
> > > +     if (bind_tx_queue(ifindex, mem->fd, &ys))
> > > +             error(1, 0, "Failed to bind\n");
> > > +
> > > +     ret = parse_address(client_ip, atoi(port), &client_sin);
> > > +     if (ret < 0)
> > > +             error(1, 0, "parse client address");
> > > +
> > > +     ret = bind(socket_fd, &client_sin, sizeof(client_sin));
> > > +     if (ret)
> > > +             error(1, ret, "bind");
> > > +
> > > +     ret = setsockopt(socket_fd, SOL_SOCKET, SO_ZEROCOPY, &opt, sizeof(opt));
> > > +     if (ret)
> > > +             error(1, ret, "set sock opt");
> > > +
> > > +     fprintf(stderr, "Connect to %s %d (via %s)\n", server_ip,
> > > +             ntohs(server_sin.sin6_port), ifname);
> > > +
> > > +     ret = connect(socket_fd, &server_sin, sizeof(server_sin));
> > > +     if (ret)
> > > +             error(1, ret, "connect");
> > > +
> > > +     while (1) {
> > > +             free(line);
> > > +             line = NULL;
> > > +             /* Subtract 1 from line_size to remove trailing newlines that
> > > +              * get_line are surely to parse...
> > > +              */
> > > +             line_size = getline(&line, &len, stdin) - 1;
> >
> > Why not send the '\n' as well? If we skip the '\n', it's not keeping
> > netcat-like behavior :-(
> >
> 
> Ah, this is to make the validation on the RX side work. The validation
> expects a repeating pattern:
> 
> 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, ....
> 
> With no newlines.
> 
> But it does become weird that TX doesn't match netcat. Let me think on
> this a bit. Maybe I can resolve this in a way where the validation
> works but also the tx side behaves like netcat. Maybe the RX
> validation can skip newlines or something. Maybe I can massage how I
> invoke the test.
> 
> This can become a rabbit hole because I do want to invoke multiple
> sendmsg() in one iteration of the test as well, and not overcomplicate
> the series.

Then let's do it for validation mode only? FWIW, my existing (python
wrapper) tests pass with your series. I'll be sending a bunch of minor
comments about the selftest part separately shortly..