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tcp_splice: Avoid awkward temporaries in tcp_splice_epoll_ctl()

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We initialise the events_a and events_b variables with
tcp_splice_conn_epoll_events() function, then immediately copy the values
into ev_a.events and ev_b.events.  We can't simply pass &ev_[ab].events to
tcp_splice_conn_epoll_events(), because struct epoll_event is packed,
leading to 'pointer may be unaligned' warnings if we attempt that.

We can, however, make tcp_splice_conn_epoll_events() take struct
epoll_event pointers rather than raw u32 pointers, avoiding the awkward
temporaries.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2023-11-07 13:42:44 +11:00 committed by Stefano Brivio
parent 409d3ca87f
commit 6357010cab
1 changed files with 11 additions and 13 deletions
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24
tcp_splice.c
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@ -95,25 +95,26 @@ static int tcp_sock_refill_ns(void *arg);
/** /**
* tcp_splice_conn_epoll_events() - epoll events masks for given state * tcp_splice_conn_epoll_events() - epoll events masks for given state
* @events: Connection event flags * @events: Connection event flags
* @a: Event mask for socket with accepted connection, set on return * @a: Event for socket with accepted connection, set on return
* @b: Event mask for connection target socket, set on return * @b: Event for connection target socket, set on return
*/ */
static void tcp_splice_conn_epoll_events(uint16_t events, static void tcp_splice_conn_epoll_events(uint16_t events,
uint32_t *a, uint32_t *b) struct epoll_event *a,
struct epoll_event *b)
{ {
*a = *b = 0; a->events = b->events = 0;
if (events & SPLICE_ESTABLISHED) { if (events & SPLICE_ESTABLISHED) {
if (!(events & B_FIN_SENT)) if (!(events & B_FIN_SENT))
*a = EPOLLIN | EPOLLRDHUP; a->events = EPOLLIN | EPOLLRDHUP;
if (!(events & A_FIN_SENT)) if (!(events & A_FIN_SENT))
*b = EPOLLIN | EPOLLRDHUP; b->events = EPOLLIN | EPOLLRDHUP;
} else if (events & SPLICE_CONNECT) { } else if (events & SPLICE_CONNECT) {
*b = EPOLLOUT; b->events = EPOLLOUT;
} }
*a |= (events & A_OUT_WAIT) ? EPOLLOUT : 0; a->events |= (events & A_OUT_WAIT) ? EPOLLOUT : 0;
*b |= (events & B_OUT_WAIT) ? EPOLLOUT : 0; b->events |= (events & B_OUT_WAIT) ? EPOLLOUT : 0;
} }
/** /**
@ -133,11 +134,8 @@ static int tcp_splice_epoll_ctl(const struct ctx *c,
.tcp.index = CONN_IDX(conn) }; .tcp.index = CONN_IDX(conn) };
struct epoll_event ev_a = { .data.u64 = ref_a.u64 }; struct epoll_event ev_a = { .data.u64 = ref_a.u64 };
struct epoll_event ev_b = { .data.u64 = ref_b.u64 }; struct epoll_event ev_b = { .data.u64 = ref_b.u64 };
uint32_t events_a, events_b;
tcp_splice_conn_epoll_events(conn->events, &events_a, &events_b); tcp_splice_conn_epoll_events(conn->events, &ev_a, &ev_b);
ev_a.events = events_a;
ev_b.events = events_b;
if (epoll_ctl(c->epollfd, m, conn->a, &ev_a) || if (epoll_ctl(c->epollfd, m, conn->a, &ev_a) ||
epoll_ctl(c->epollfd, m, conn->b, &ev_b)) { epoll_ctl(c->epollfd, m, conn->b, &ev_b)) {