diff options
Diffstat (limited to 'results/classifier/zero-shot/108/debug/2553')
| -rw-r--r-- | results/classifier/zero-shot/108/debug/2553 | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/results/classifier/zero-shot/108/debug/2553 b/results/classifier/zero-shot/108/debug/2553 new file mode 100644 index 000000000..119ae6fea --- /dev/null +++ b/results/classifier/zero-shot/108/debug/2553 @@ -0,0 +1,97 @@ +debug: 0.967 +performance: 0.960 +network: 0.957 +device: 0.949 +graphic: 0.945 +PID: 0.945 +socket: 0.933 +other: 0.931 +boot: 0.930 +files: 0.923 +permissions: 0.916 +semantic: 0.912 +KVM: 0.869 +vnc: 0.863 + +Joining IP multicast fails when emulating 64-bit Linux +Description of problem: +I have some code that joins IP multicast groups and I'd like to use QEMU to test it on big-endian and/or 32-bit platforms. But when I compile it for 64-bit big-endian platforms (e.g. PowerPC64) and run it under QEMU user-mode emulation, the setsockopt(IP_ADD_MEMBERSHIP) call fails with ENODEV. + +This appears to refer to the imr_ifindex ("interface index") field in struct ip_mreqn not being valid, which in turn appears to be because it's not being correctly marshalled from the binary under emulation, to the host's *actual* setsockopt system call. + +I *think* this may be because linux-user/syscall_defs.h (https://github.com/qemu/qemu/blob/master/linux-user/syscall_defs.h) contains the following at line 210: + +``` +struct target_ip_mreqn { + struct target_in_addr imr_multiaddr; + struct target_in_addr imr_address; + abi_long imr_ifindex; +}; +``` + +but the actual Linux ip_mreqn has imr_ifindex as an int (32-bit everywhere) not a long (64-bit on PPC64); the size of this structure is 12 on all Linux platforms. + +I opted to submit an issue instead of just patching it, in case there was some wider context I hadn't seen? +Steps to reproduce: +1. take the following C program (distilled from a larger program): + +``` +#include <sys/types.h> +#include <sys/socket.h> +#include <netinet/in.h> +#include <arpa/inet.h> +#include <stdio.h> +#include <stdlib.h> + +int main(int argc, char *argv[]) +{ + int fd = socket(AF_INET, SOCK_DGRAM, 0); + if (fd < 0) { + perror("socket"); + return 1; + } + + struct ip_mreqn mreq; + mreq.imr_multiaddr.s_addr = inet_addr("239.255.255.250"); + mreq.imr_address.s_addr = htonl(INADDR_ANY); + mreq.imr_ifindex = 1; + int size = sizeof(mreq); + printf("size=%u\n", size); + if (setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, + (char*) &mreq, sizeof(mreq)) < 0) { + perror("setsockopt"); + return 1; + } + printf("OK\n"); + return 0; +} +``` + +2. confirm it works compiled native on amd64/x86_64: + +``` +[peter@amd64 misc]$ gcc mcast.c -o mcast +[peter@amd64 misc]$ ./mcast +size=12 +OK +``` + +3. watch it *not* work emulated: + +``` +[peter@amd64 misc]$ powerpc64-linux-gnu-gcc mcast.c -o mcast.ppc64 +[peter@amd64 misc]$ QEMU_LD_PREFIX=/usr/powerpc64-linux-gnu qemu-ppc64 ./mcast.ppc64 +size=12 +setsockopt: No such device +``` +Additional information: +If the target_ip_mreqn issue is real, the following code in syscall.c helped conceal it: + + if (optlen < sizeof (struct target_ip_mreq) || + optlen > sizeof (struct target_ip_mreqn)) { + return -TARGET_EINVAL; + } + +Should this instead be testing for size equal to target_ip_mreq or equal to target_ip_mreqn, not anywhere in between? in this case target_ip_mreq is 8 bytes, target_ip_mreqn is 16 bytes, but optlen is 12. The end result is that QEMU passes 4 bytes of uninitialised stack memory as imr_ifindex! + +The actual kernel behaviour appears to be: smaller than ip_mreq, EINVAL; between ip_mreq and ip_mreqn, silently treat as ip_mreq; larger or equal to ip_mreqn, silently treat as ip_mreqn. see https://github.com/torvalds/linux/blob/b31c4492884252a8360f312a0ac2049349ddf603/net/ipv4/ip_sockglue.c#L1234 |