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netlink: refactor control data generation for recvmsg(2)

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Netlink should return a very simple control data on every recvmsg(2)
syscall.  This data is associated with a syscall, not with an nlmsg,
neither with internal our internal representation (nl_bufs).  There is
no need to pre-allocate it in non-sleepable context and attach to
nl_buf.  Allocate right in the syscall with M_WAITOK.  This also
shaves lots of code and simplifies things.

Reviewed by:		melifaro
Differential Revision:	https://reviews.freebsd.org/D42989
This commit is contained in:
Gleb Smirnoff 2024-01-02 13:05:46 -08:00
parent 7e19c0186f
commit ff5ad900d2
3 changed files with 34 additions and 75 deletions
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64
sys/netlink/netlink_domain.c
View file

@ -179,15 +179,6 @@ nl_get_groups_compat(struct nlpcb *nlp)
return (groups_mask);
}
static void
nl_send_one_group(struct nl_writer *nw, struct nl_buf *nb, struct nlpcb *nlp)
{
if (__predict_false(nlp->nl_flags & NLF_MSG_INFO))
nl_add_msg_info(nb);
nw->buf = nb;
(void)nl_send_one(nw);
}
static struct nl_buf *
nl_buf_copy(struct nl_buf *nb)
{
@ -197,13 +188,6 @@ nl_buf_copy(struct nl_buf *nb)
if (__predict_false(copy == NULL))
return (NULL);
memcpy(copy, nb, sizeof(*nb) + nb->buflen);
if (nb->control != NULL) {
copy->control = m_copym(nb->control, 0, M_COPYALL, M_NOWAIT);
if (__predict_false(copy->control == NULL)) {
nl_buf_free(copy);
return (NULL);
}
}
return (copy);
}
@ -248,7 +232,8 @@ nl_send_group(struct nl_writer *nw)
copy = nl_buf_copy(nb);
if (copy != NULL) {
nl_send_one_group(nw, copy, nlp_last);
nw->buf = copy;
(void)nl_send_one(nw);
} else {
NLP_LOCK(nlp_last);
if (nlp_last->nl_socket != NULL)
@ -259,9 +244,10 @@ nl_send_group(struct nl_writer *nw)
nlp_last = nlp;
}
}
if (nlp_last != NULL)
nl_send_one_group(nw, nb, nlp_last);
else
if (nlp_last != NULL) {
nw->buf = nb;
(void)nl_send_one(nw);
} else
nl_buf_free(nb);
NLCTL_RUNLOCK(ctl);
@ -657,6 +643,30 @@ nl_sosend(struct socket *so, struct sockaddr *addr, struct uio *uio,
return (error);
}
/* Create control data for recvmsg(2) on Netlink socket. */
static struct mbuf *
nl_createcontrol(struct nlpcb *nlp)
{
struct {
struct nlattr nla;
uint32_t val;
} data[] = {
{
.nla.nla_len = sizeof(struct nlattr) + sizeof(uint32_t),
.nla.nla_type = NLMSGINFO_ATTR_PROCESS_ID,
.val = nlp->nl_process_id,
},
{
.nla.nla_len = sizeof(struct nlattr) + sizeof(uint32_t),
.nla.nla_type = NLMSGINFO_ATTR_PORT_ID,
.val = nlp->nl_port,
},
};
return (sbcreatecontrol(data, sizeof(data), NETLINK_MSG_INFO,
SOL_NETLINK, M_WAITOK));
}
static int
nl_soreceive(struct socket *so, struct sockaddr **psa, struct uio *uio,
struct mbuf **mp, struct mbuf **controlp, int *flagsp)
@ -667,6 +677,7 @@ nl_soreceive(struct socket *so, struct sockaddr **psa, struct uio *uio,
.nl_pid = 0 /* comes from the kernel */
};
struct sockbuf *sb = &so->so_rcv;
struct nlpcb *nlp = sotonlpcb(so);
struct nl_buf *first, *last, *nb, *next;
struct nlmsghdr *hdr;
int flags, error;
@ -681,6 +692,9 @@ nl_soreceive(struct socket *so, struct sockaddr **psa, struct uio *uio,
*psa = sodupsockaddr((const struct sockaddr *)&nl_empty_src,
M_WAITOK);
if (controlp != NULL && (nlp->nl_flags & NLF_MSG_INFO))
*controlp = nl_createcontrol(nlp);
flags = flagsp != NULL ? *flagsp & ~MSG_TRUNC : 0;
trunc = flagsp != NULL ? *flagsp & MSG_TRUNC : false;
nonblock = (so->so_state & SS_NBIO) ||
@ -691,9 +705,6 @@ nl_soreceive(struct socket *so, struct sockaddr **psa, struct uio *uio,
if (__predict_false(error))
return (error);
if (controlp != NULL)
*controlp = NULL;
len = 0;
overflow = 0;
msgrcv = 0;
@ -798,13 +809,6 @@ nl_soreceive(struct socket *so, struct sockaddr **psa, struct uio *uio,
for (nb = first; nb != last; nb = next) {
next = TAILQ_NEXT(nb, tailq);
/* XXXGL multiple controls??? */
if (controlp != NULL && *controlp == NULL &&
nb->control != NULL && !peek) {
*controlp = nb->control;
nb->control = NULL;
}
if (__predict_true(error == 0))
error = uiomove(&nb->data[nb->offset],
(int)(nb->datalen - nb->offset), uio);

43
sys/netlink/netlink_io.c
View file

@ -62,7 +62,6 @@ nl_buf_alloc(size_t len, int mflag)
if (__predict_true(nb != NULL)) {
nb->buflen = len;
nb->datalen = nb->offset = 0;
nb->control = NULL;
}
return (nb);
@ -72,51 +71,9 @@ void
nl_buf_free(struct nl_buf *nb)
{
if (nb->control)
m_freem(nb->control);
free(nb, M_NETLINK);
}
void
nl_add_msg_info(struct nl_buf *nb)
{
/* XXXGL pass nlp as arg? */
struct nlpcb *nlp = nl_get_thread_nlp(curthread);
NL_LOG(LOG_DEBUG2, "Trying to recover nlp from thread %p: %p",
curthread, nlp);
if (nlp == NULL)
return;
/* Prepare what we want to encode - PID, socket PID & msg seq */
struct {
struct nlattr nla;
uint32_t val;
} data[] = {
{
.nla.nla_len = sizeof(struct nlattr) + sizeof(uint32_t),
.nla.nla_type = NLMSGINFO_ATTR_PROCESS_ID,
.val = nlp->nl_process_id,
},
{
.nla.nla_len = sizeof(struct nlattr) + sizeof(uint32_t),
.nla.nla_type = NLMSGINFO_ATTR_PORT_ID,
.val = nlp->nl_port,
},
};
nb->control = sbcreatecontrol(data, sizeof(data),
NETLINK_MSG_INFO, SOL_NETLINK, M_NOWAIT);
if (__predict_true(nb->control != NULL))
NL_LOG(LOG_DEBUG2, "Storing %u bytes of control data, ctl: %p",
(unsigned)sizeof(data), nb->control);
else
NL_LOG(LOG_DEBUG2, "Failed to allocate %u bytes of control",
(unsigned)sizeof(data));
}
void
nl_schedule_taskqueue(struct nlpcb *nlp)
{

2
sys/netlink/netlink_var.h
View file

@ -45,7 +45,6 @@ struct ucred;
struct nl_buf {
TAILQ_ENTRY(nl_buf) tailq;
struct mbuf *control;
u_int buflen;
u_int datalen;
u_int offset;
@ -142,7 +141,6 @@ void nl_taskqueue_handler(void *_arg, int pending);
void nl_schedule_taskqueue(struct nlpcb *nlp);
void nl_process_receive_locked(struct nlpcb *nlp);
void nl_set_source_metadata(struct mbuf *m, int num_messages);
void nl_add_msg_info(struct nl_buf *nb);
struct nl_buf *nl_buf_alloc(size_t len, int mflag);
void nl_buf_free(struct nl_buf *nb);