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sctp: add sctp_make_op_error_limited and reuse inner functions
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The idea is quite similar to the old functions, but note that the _fixed
function wasn't "fixed" as in that it would generate a packet with a fixed
size, but rather limited/bounded to PMTU.

Also, now with sctp_mtu_payload(), we have a more accurate limit.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Marcelo Ricardo Leitner authored and David S. Miller committed May 1, 2018
1 parent 6d3e8aa commit 8914f4b
Showing 1 changed file with 46 additions and 84 deletions.
130 changes: 46 additions & 84 deletions net/sctp/sm_make_chunk.c
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Original file line number Diff line number Diff line change
Expand Up @@ -81,8 +81,6 @@ static int sctp_process_param(struct sctp_association *asoc,
gfp_t gfp);
static void *sctp_addto_param(struct sctp_chunk *chunk, int len,
const void *data);
static void *sctp_addto_chunk_fixed(struct sctp_chunk *, int len,
const void *data);

/* Control chunk destructor */
static void sctp_control_release_owner(struct sk_buff *skb)
Expand Down Expand Up @@ -154,9 +152,8 @@ static const struct sctp_paramhdr prsctp_param = {
cpu_to_be16(sizeof(struct sctp_paramhdr)),
};

/* A helper to initialize an op error inside a
* provided chunk, as most cause codes will be embedded inside an
* abort chunk.
/* A helper to initialize an op error inside a provided chunk, as most
* cause codes will be embedded inside an abort chunk.
*/
int sctp_init_cause(struct sctp_chunk *chunk, __be16 cause_code,
size_t paylen)
Expand All @@ -177,29 +174,6 @@ int sctp_init_cause(struct sctp_chunk *chunk, __be16 cause_code,
return 0;
}

/* A helper to initialize an op error inside a
* provided chunk, as most cause codes will be embedded inside an
* abort chunk. Differs from sctp_init_cause in that it won't oops
* if there isn't enough space in the op error chunk
*/
static int sctp_init_cause_fixed(struct sctp_chunk *chunk, __be16 cause_code,
size_t paylen)
{
struct sctp_errhdr err;
__u16 len;

/* Cause code constants are now defined in network order. */
err.cause = cause_code;
len = sizeof(err) + paylen;
err.length = htons(len);

if (skb_tailroom(chunk->skb) < len)
return -ENOSPC;

chunk->subh.err_hdr = sctp_addto_chunk_fixed(chunk, sizeof(err), &err);

return 0;
}
/* 3.3.2 Initiation (INIT) (1)
*
* This chunk is used to initiate a SCTP association between two
Expand Down Expand Up @@ -1263,20 +1237,26 @@ static struct sctp_chunk *sctp_make_op_error_space(
return retval;
}

/* Create an Operation Error chunk of a fixed size,
* specifically, max(asoc->pathmtu, SCTP_DEFAULT_MAXSEGMENT)
* This is a helper function to allocate an error chunk for
* for those invalid parameter codes in which we may not want
* to report all the errors, if the incoming chunk is large
/* Create an Operation Error chunk of a fixed size, specifically,
* min(asoc->pathmtu, SCTP_DEFAULT_MAXSEGMENT) - overheads.
* This is a helper function to allocate an error chunk for for those
* invalid parameter codes in which we may not want to report all the
* errors, if the incoming chunk is large. If it can't fit in a single
* packet, we ignore it.
*/
static inline struct sctp_chunk *sctp_make_op_error_fixed(
static inline struct sctp_chunk *sctp_make_op_error_limited(
const struct sctp_association *asoc,
const struct sctp_chunk *chunk)
{
size_t size = asoc ? asoc->pathmtu : 0;
size_t size = SCTP_DEFAULT_MAXSEGMENT;
struct sctp_sock *sp = NULL;

if (asoc) {
size = min_t(size_t, size, asoc->pathmtu);
sp = sctp_sk(asoc->base.sk);
}

if (!size)
size = SCTP_DEFAULT_MAXSEGMENT;
size = sctp_mtu_payload(sp, size, sizeof(struct sctp_errhdr));

return sctp_make_op_error_space(asoc, chunk, size);
}
Expand Down Expand Up @@ -1528,18 +1508,6 @@ void *sctp_addto_chunk(struct sctp_chunk *chunk, int len, const void *data)
return target;
}

/* Append bytes to the end of a chunk. Returns NULL if there isn't sufficient
* space in the chunk
*/
static void *sctp_addto_chunk_fixed(struct sctp_chunk *chunk,
int len, const void *data)
{
if (skb_tailroom(chunk->skb) >= len)
return sctp_addto_chunk(chunk, len, data);
else
return NULL;
}

/* Append bytes from user space to the end of a chunk. Will panic if
* chunk is not big enough.
* Returns a kernel err value.
Expand Down Expand Up @@ -1834,6 +1802,9 @@ struct sctp_association *sctp_unpack_cookie(
kt = ktime_get_real();

if (!asoc && ktime_before(bear_cookie->expiration, kt)) {
suseconds_t usecs = ktime_to_us(ktime_sub(kt, bear_cookie->expiration));
__be32 n = htonl(usecs);

/*
* Section 3.3.10.3 Stale Cookie Error (3)
*
Expand All @@ -1842,17 +1813,12 @@ struct sctp_association *sctp_unpack_cookie(
* Stale Cookie Error: Indicates the receipt of a valid State
* Cookie that has expired.
*/
len = ntohs(chunk->chunk_hdr->length);
*errp = sctp_make_op_error_space(asoc, chunk, len);
if (*errp) {
suseconds_t usecs = ktime_to_us(ktime_sub(kt, bear_cookie->expiration));
__be32 n = htonl(usecs);

sctp_init_cause(*errp, SCTP_ERROR_STALE_COOKIE,
sizeof(n));
sctp_addto_chunk(*errp, sizeof(n), &n);
*errp = sctp_make_op_error(asoc, chunk,
SCTP_ERROR_STALE_COOKIE, &n,
sizeof(n), 0);
if (*errp)
*error = -SCTP_IERROR_STALE_COOKIE;
} else
else
*error = -SCTP_IERROR_NOMEM;

goto fail;
Expand Down Expand Up @@ -2003,12 +1969,8 @@ static int sctp_process_hn_param(const struct sctp_association *asoc,
if (*errp)
sctp_chunk_free(*errp);

*errp = sctp_make_op_error_space(asoc, chunk, len);

if (*errp) {
sctp_init_cause(*errp, SCTP_ERROR_DNS_FAILED, len);
sctp_addto_chunk(*errp, len, param.v);
}
*errp = sctp_make_op_error(asoc, chunk, SCTP_ERROR_DNS_FAILED,
param.v, len, 0);

/* Stop processing this chunk. */
return 0;
Expand Down Expand Up @@ -2133,23 +2095,23 @@ static enum sctp_ierror sctp_process_unk_param(
/* Make an ERROR chunk, preparing enough room for
* returning multiple unknown parameters.
*/
if (NULL == *errp)
*errp = sctp_make_op_error_fixed(asoc, chunk);

if (*errp) {
if (!sctp_init_cause_fixed(*errp, SCTP_ERROR_UNKNOWN_PARAM,
SCTP_PAD4(ntohs(param.p->length))))
sctp_addto_chunk_fixed(*errp,
SCTP_PAD4(ntohs(param.p->length)),
param.v);
} else {
/* If there is no memory for generating the ERROR
* report as specified, an ABORT will be triggered
* to the peer and the association won't be
* established.
*/
retval = SCTP_IERROR_NOMEM;
if (!*errp) {
*errp = sctp_make_op_error_limited(asoc, chunk);
if (!*errp) {
/* If there is no memory for generating the
* ERROR report as specified, an ABORT will be
* triggered to the peer and the association
* won't be established.
*/
retval = SCTP_IERROR_NOMEM;
break;
}
}

if (!sctp_init_cause(*errp, SCTP_ERROR_UNKNOWN_PARAM,
ntohs(param.p->length)))
sctp_addto_chunk(*errp, ntohs(param.p->length),
param.v);
break;
default:
break;
Expand Down Expand Up @@ -2225,10 +2187,10 @@ static enum sctp_ierror sctp_verify_param(struct net *net,
* MUST be aborted. The ABORT chunk SHOULD contain the error
* cause 'Protocol Violation'.
*/
if (SCTP_AUTH_RANDOM_LENGTH !=
ntohs(param.p->length) - sizeof(struct sctp_paramhdr)) {
if (SCTP_AUTH_RANDOM_LENGTH != ntohs(param.p->length) -
sizeof(struct sctp_paramhdr)) {
sctp_process_inv_paramlength(asoc, param.p,
chunk, err_chunk);
chunk, err_chunk);
retval = SCTP_IERROR_ABORT;
}
break;
Expand Down

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