This is merely a historical archive of years 2008-2021, before the migration to mailman3.
A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/gerrit-log@lists.osmocom.org/.
laforge gerrit-no-reply at lists.osmocom.orglaforge has uploaded this change for review. ( https://gerrit.osmocom.org/c/libosmo-netif/+/18628 ) Change subject: src/stream: Work around more Linux kernel ABI breakage ...................................................................... src/stream: Work around more Linux kernel ABI breakage Back in Change-Id Ia95dd1f9ffed9f743c049e05797b1a6f1f9f8c69 we tried to work-around kernel ABI breakage introduced in kernel >= v5.5, but it seems that there have already been similar ABI breakages in v4.11 and v4.12. See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/uapi/linux/sctp.h?id=b6e6b5f1da7e8d092f86a4351802c27c0170c5a5 and https://marc.info/?l=linux-sctp&m=158729301516157&w=2 for the ost recent incarnation. See https://osmocom.org/issues/4573#note-6 for all known cases of SCTP_EVENTS ABI breakage. Change-Id: Icc49f347cdc0bb77a5c0e230597d662ac35b4acc --- M src/stream.c 1 file changed, 71 insertions(+), 20 deletions(-) git pull ssh://gerrit.osmocom.org:29418/libosmo-netif refs/changes/28/18628/1 diff --git a/src/stream.c b/src/stream.c index 6e4c461..6b8f5a0 100644 --- a/src/stream.c +++ b/src/stream.c @@ -73,6 +73,75 @@ #define MSG_NOSIGNAL 0 #endif +/* is any of the bytes from offset .. size in 'u8' non-zero? */ +static bool byte_nonzero(const uint8_t *u8, unsigned int offset, unsigned int u8_size) +{ + int j; + + for (j = offset; j < u8_size; j++) { + if (u8[j] != 0) + return true; + } + + return false; +} + +/* Attempt to work around Linux kernel ABI breakage + * + * The Linux kernel ABI for the SCTP_EVENTS socket option has been broken repeatedly. + * - until commit 35ea82d611da59f8bea44a37996b3b11bb1d3fd7 ( kernel < 4.11), the size is 10 bytes + * - in 4.11 it is 11 bytes + * - in 4.12 .. 5.4 it is 13 bytes + * - in kernels >= 5.5 it is 14 bytes + * + * This wouldn't be a problem if the kernel didn't have a "stupid" assumption that the structure + * size passed by userspace will match 1:1 the length of the structure at kernel compile time. In + * an ideal world, it would just use the known first bytes and assume the remainder is all zero. + * But as it doesn't do that, let's try to work around this */ +static int sctp_setsockopt_events_linux_workaround(int fd, const struct sctp_event_subscribe *event) +{ + unsigned int size = sizeof(*event); + const uint8_t try_sizes[] = { 14, 13, 11, 10 }; + uint8_t buf[14]; + int rc, i; + + /* first try to use the userspace structure as-is */ + rc = setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, event, sizeof(*event)); + if (rc != -EINVAL) + return rc; + + /* next, try with shorter sizes (older kernel + new userspace headers) */ + for (i = 0; i < ARRAY_SIZE(try_sizes); i++) { + if (try_sizes[i] >= size) + continue; + + /* ensure that if the caller requested one of the "later" options we don't + * truncate */ + if (byte_nonzero((const uint8_t *)event, try_sizes[i], size)) + continue; + + rc = setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, event, try_sizes[i]); + if (rc != -EINVAL) + return rc; + } + + /* finally, try with larger sizes (newer kernel + old userspace headers) */ + if (size < sizeof(buf)) { + memset(buf, 0, sizeof(buf)); + memcpy(buf, event, size); + for (i = 0; i < ARRAY_SIZE(try_sizes); i++) { + if (try_sizes[i] < size) + continue; + + rc = setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, buf, try_sizes[i]); + if (rc != -EINVAL) + return rc; + } + } + + return rc; +} + static int sctp_sock_activate_events(int fd) { #ifdef HAVE_LIBSCTP @@ -89,28 +158,10 @@ event.sctp_shutdown_event = 1; /* IMPORTANT: Do NOT enable sender_dry_event here, see * https://bugzilla.redhat.com/show_bug.cgi?id=1442784 */ - rc = setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, - &event, sizeof(event)); - /* - * Attempt to work around kernel ABI breakage - * - * In kernel commit b6e6b5f1da7e8d092f86a4351802c27c0170c5a5, the - * struct sctp_event_subscribe had a u8 field added to it at the end, thus - * breaking ABI. - * See https://marc.info/?l=linux-sctp&m=158729301516157&w=2 for discussion. - * - * We attempt to work around the issue where the kernel header are new - * and running kernel is old, by forcing the size of the struct to 13 which - * is the "old" size - */ - if ((rc < 0) && (sizeof(event) != 13)) - rc = setsockopt(fd, IPPROTO_SCTP, SCTP_EVENTS, - &event, 13); - + rc = sctp_setsockopt_events_linux_workaround(fd, &event); if (rc < 0) - LOGP(DLINP, LOGL_ERROR, "couldn't activate SCTP events " - "on FD %u\n", fd); + LOGP(DLINP, LOGL_ERROR, "couldn't activate SCTP events on FD %u\n", fd); return rc; #else return -1; -- To view, visit https://gerrit.osmocom.org/c/libosmo-netif/+/18628 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: libosmo-netif Gerrit-Branch: master Gerrit-Change-Id: Icc49f347cdc0bb77a5c0e230597d662ac35b4acc Gerrit-Change-Number: 18628 Gerrit-PatchSet: 1 Gerrit-Owner: laforge <laforge at osmocom.org> Gerrit-MessageType: newchange -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/gerrit-log/attachments/20200601/320d0578/attachment.htm>