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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20230331160914.1608208-34-dhowells@redhat.com> References: <20230331160914.1608208-34-dhowells@redhat.com> <20230331160914.1608208-1-dhowells@redhat.com> To: Tom Herbert , Tom Herbert Cc: dhowells@redhat.com, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Al Viro , Christoph Hellwig , Jens Axboe , Jeff Layton , Christian Brauner , Chuck Lever III , Linus Torvalds , netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Is AF_KCM functional? MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1817940.1680514468.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Mon, 03 Apr 2023 10:34:28 +0100 Message-ID: <1817941.1680514468@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Rspamd-Queue-Id: 2B5A1140018 X-Stat-Signature: n9dbaqdr339ek6dbgx63udf6iaqthzgi X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1680514476-657056 X-HE-Meta: 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 9LOB1Ru9 h8A2XYy6m/RScRAyjWSPi0h6ALBcXYsbMRfn0Mr+toYAmM3N2TiIAiTySzWjQ6FQnuLZHyL9EdbcKqWFw0Pes0hGMQwHhznLA5RI9o/enwDeb6DvgziUWb2AoTek3RJaWroZ/g0ow3v8KWmwX1sX9PO9s1GDRjsOq6U1UCJuMJHjdZ6mqTGt+U1+Jg3Vsi0DKwPnWG6tecdpnEOI2qmi9AslC+u71b4zW1XwygzidGwx8PEXhUrBYF96qMfMM1RNoo7JuTqe+1RpROARFLawueut6VFA1BdDXs2GA X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Okay, I have a test program for AF_KCM that builds and works up to a point= . However, it doesn't seem to work for two reasons: (1) When it clones a socket with SIOCKCMCLONE, it doesn't set the LSM con= text on the new socket. This results in EACCES if, say, SELinux is enforc= ing. ioctl(8, SIOCPROTOPRIVATE, 0x7ffe17cc3b24) =3D 0 ioctl(9, SIOCPROTOPRIVATE, 0x7ffe17cc3b24) =3D -1 EACCES (Permission deni= ed) from the SIOCKCMATTACH ioctl, so this won't work on a number of Linux distributions, such as Fedora and RHEL. (2) Assuming SELinux is set to non-enforcing mode, it then fails when try= ing to attach the cloned KCM socket to the TCP socket: ioctl(8, SIOCPROTOPRIVATE, 0x7ffddfb64f84) =3D 0 ioctl(9, SIOCPROTOPRIVATE, 0x7ffddfb64f84) =3D -1 EALREADY (Operation alr= eady in progress) again from the SIOCKCMATTACH ioctl. This seems to be because the TCP socket (csock in kcm_attach() in the kernel) has already got sk_user_= data set from the first ioctl on fd 8: if (csk->sk_user_data) { write_unlock_bh(&csk->sk_callback_lock); kmem_cache_free(kcm_psockp, psock); err =3D -EALREADY; goto out; } Now, this could be a bug in the test program. Since both fds 8 and 9 shou= ld correspond to the same multiplexor, presumably the TCP socket only needs attaching once (note that the TCP socket is obtained from accept() in this case). David --- /* * A sample program of KCM. * * $ gcc -lbcc kcm-sample.c * $ ./a.out 10000 * * https://gist.github.com/dhowells/24b87fdf731884ed9ca19e9840c0c894 */ #include #include #include #include #include #include #include #include #include #include #include #include #include /* libbcc */ #include #include #include #include /* From linux/kcm.h */ struct kcm_clone { int fd; }; struct kcm_attach { int fd; int bpf_fd; }; #ifndef AF_KCM /* From linux/socket.h */ #define AF_KCM 41 /* Kernel Connection Multiplexor*/ #endif #ifndef KCMPROTO_CONNECTED /* From linux/kcm.h */ #define KCMPROTO_CONNECTED 0 #endif #ifndef SIOCKCMCLONE /* From linux/sockios.h */ #define SIOCPROTOPRIVATE 0x89E0 /* to 89EF */ /* From linux/kcm.h */ #define SIOCKCMATTACH (SIOCPROTOPRIVATE + 0) #define SIOCKCMCLONE (SIOCPROTOPRIVATE + 2) #endif struct my_proto { struct _hdr { uint32_t len; } hdr; char data[32]; }; const char *bpf_prog_string =3D " \ ssize_t bpf_prog1(struct __sk_buff *skb) \ { \ return load_half(skb, 0) + 4; \ } \ "; int servsock_init(int port) { int s, error; struct sockaddr_in addr; s =3D socket(AF_INET, SOCK_STREAM, 0); addr.sin_family =3D AF_INET; addr.sin_port =3D htons(port); addr.sin_addr.s_addr =3D INADDR_ANY; error =3D bind(s, (struct sockaddr *)&addr, sizeof(addr)); if (error =3D=3D -1) err(EXIT_FAILURE, "bind"); error =3D listen(s, 10); if (error =3D=3D -1) err(EXIT_FAILURE, "listen"); return s; } int bpf_init(void) { int fd, map_fd; void *mod; int key; long long value =3D 0; mod =3D bpf_module_create_c_from_string(bpf_prog_string, 0, NULL, 0, 0, N= ULL); fd =3D bcc_prog_load( BPF_PROG_TYPE_SOCKET_FILTER, "bpf_prog1", bpf_function_start(mod, "bpf_prog1"), bpf_function_size(mod, "bpf_prog1"), bpf_module_license(mod), bpf_module_kern_version(mod), 0, NULL, 0); if (fd =3D=3D -1) exit(1); return fd; } void client(int port) { int s, error; struct sockaddr_in addr; struct hostent *host; struct my_proto my_msg; int len; printf("client is starting\n"); s =3D socket(AF_INET, SOCK_STREAM, 0); if (s =3D=3D -1) err(EXIT_FAILURE, "socket"); memset(&addr, 0, sizeof(addr)); addr.sin_family =3D AF_INET; addr.sin_port =3D htons(port); host =3D gethostbyname("localhost"); if (host =3D=3D NULL) err(EXIT_FAILURE, "gethostbyname"); memcpy(&addr.sin_addr, host->h_addr, host->h_length); error =3D connect(s, (struct sockaddr *)&addr, sizeof(addr)); if (error =3D=3D -1) err(EXIT_FAILURE, "connect"); len =3D sprintf(my_msg.data, "hello"); my_msg.data[len] =3D '\0'; my_msg.hdr.len =3D htons(len + 1); len =3D write(s, &my_msg, sizeof(my_msg.hdr) + len + 1); if (error =3D=3D -1) err(EXIT_FAILURE, "write"); printf("client sent data\n"); printf("client is waiting a reply\n"); len =3D read(s, &my_msg, sizeof(my_msg)); if (error =3D=3D -1) err(EXIT_FAILURE, "read"); printf("\"%s\" from server\n", my_msg.data); printf("client received data\n"); close(s); } int kcm_init(void) { int kcmfd; kcmfd =3D socket(AF_KCM, SOCK_DGRAM, KCMPROTO_CONNECTED); if (kcmfd =3D=3D -1) err(EXIT_FAILURE, "socket(AF_KCM)"); return kcmfd; } int kcm_clone(int kcmfd) { int error; struct kcm_clone clone_info; memset(&clone_info, 0, sizeof(clone_info)); error =3D ioctl(kcmfd, SIOCKCMCLONE, &clone_info); if (error =3D=3D -1) err(EXIT_FAILURE, "ioctl(SIOCKCMCLONE)"); return clone_info.fd; } int kcm_attach(int kcmfd, int csock, int bpf_prog_fd) { int error; struct kcm_attach attach_info; memset(&attach_info, 0, sizeof(attach_info)); attach_info.fd =3D csock; attach_info.bpf_fd =3D bpf_prog_fd; error =3D ioctl(kcmfd, SIOCKCMATTACH, &attach_info); if (error =3D=3D -1) err(EXIT_FAILURE, "ioctl(SIOCKCMATTACH)"); } void process(int kcmfd0, int kcmfd1) { struct my_proto my_msg; int error, len; struct pollfd fds[2]; struct msghdr msg; struct iovec iov; int fd; fds[0].fd =3D kcmfd0; fds[0].events =3D POLLIN; fds[0].revents =3D 0; fds[1].fd =3D kcmfd1; fds[1].events =3D POLLIN; fds[1].revents =3D 0; printf("server is waiting data\n"); error =3D poll(fds, 1, -1); if (error =3D=3D -1) err(EXIT_FAILURE, "poll"); if (fds[0].revents & POLLIN) fd =3D fds[0].fd; else if (fds[1].revents & POLLIN) fd =3D fds[1].fd; iov.iov_base =3D &my_msg; iov.iov_len =3D sizeof(my_msg); memset(&msg, 0, sizeof(msg)); msg.msg_iov =3D &iov; msg.msg_iovlen =3D 1; printf("server is receiving data\n"); len =3D recvmsg(fd, &msg, 0); if (len =3D=3D -1) err(EXIT_FAILURE, "recvmsg"); printf("\"%s\" from client\n", my_msg.data); printf("server received data\n"); len =3D sprintf(my_msg.data, "goodbye"); my_msg.data[len] =3D '\0'; my_msg.hdr.len =3D htons(len + 1); len =3D sendmsg(fd, &msg, 0); if (len =3D=3D -1) err(EXIT_FAILURE, "sendmsg"); } void server(int tcpfd, int bpf_prog_fd) { int kcmfd0, error, kcmfd1; struct sockaddr_in client; int len, csock; printf("server is starting\n"); kcmfd0 =3D kcm_init(); kcmfd1 =3D kcm_clone(kcmfd0); len =3D sizeof(client); csock =3D accept(tcpfd, (struct sockaddr *)&client, &len); if (csock =3D=3D -1) err(EXIT_FAILURE, "accept"); kcm_attach(kcmfd0, csock, bpf_prog_fd); kcm_attach(kcmfd1, csock, bpf_prog_fd); process(kcmfd0, kcmfd1); close(kcmfd0); close(kcmfd1); } int main(int argc, char **argv) { int error, tcpfd, bpf_prog_fd; pid_t pid; int pipefd[2]; int dummy; if (argc !=3D 2) { fprintf(stderr, "Format %s \n", argv[0]); exit(2); } error =3D pipe(pipefd); if (error =3D=3D -1) err(EXIT_FAILURE, "pipe"); pid =3D fork(); if (pid =3D=3D -1) err(EXIT_FAILURE, "fork"); if (pid =3D=3D 0) { /* wait for server's ready */ read(pipefd[0], &dummy, sizeof(dummy)); client(atoi(argv[1])); exit(0); } tcpfd =3D servsock_init(atoi(argv[1])); bpf_prog_fd =3D bpf_init(); /* tell ready */ write(pipefd[1], &dummy, sizeof(dummy)); server(tcpfd, bpf_prog_fd); waitpid(pid, NULL, 0); close(bpf_prog_fd); close(tcpfd); return 0; }