BTW, the subjects for the tracing subsystem should always start with a
capital letter.
"tracing: Support IPv6 filter predicates"
But that's not why I'm replying here.
On Fri, 28 Apr 2023 16:34:46 +0100
Alan Maguire <alan.maguire@xxxxxxxxxx> wrote:
> Support '==' and '!=' predicates for IPv6 addresses;
> for example
>
> cd /sys/kernel/debug/tracing/events/tcp/tcp_receive_reset
> echo "saddr_v6 == ::1" > filter
>
> or equivalently
>
> echo "saddr_v6 == 0:0:0:0:0:0:0:1" > filter
>
> Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
> ---
> kernel/trace/trace_events_filter.c | 73 ++++++++++++++++++++++++++++++
> 1 file changed, 73 insertions(+)
>
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index d8e08d3c3594..e2521574f3c4 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -1665,6 +1665,79 @@ static int parse_pred(const char *str, void *data,
> if (pred->op == OP_NE)
> pred->not = 1;
>
> + } else if (field->size == 16 &&
> + (str[i] == ':' ||
> + (isalnum(str[i]) && tolower(str[i + 1]) != 'x'))) {
> + u8 j, gap_size, gap = 0, gap_count = 0, index = 0;
> + u16 tmp_v6addr[8] = {};
> + u16 v6addr[8] = {};
> +
> + /* For IPv6 addresses, only '==' or '!=' are supported. */
> + if (pred->op != OP_EQ && pred->op != OP_NE) {
> + parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i);
> + goto err_free;
> + }
> + /* Store the u16s in the address string consecutively in
> + * tmp_v6addr while tracking the presence of a "::" (if any)
> + * in the IPv6 address string; we will use its location
> + * to determine how many u16s it represents (the gap_size
> + * below). Only one "::" is allowed in an IPv6 address
> + * string.
> + */
> + while (isalnum(str[i]) || str[i] == ':') {
> + switch (str[i]) {
> + case ':':
> + i++;
> + /* mark "::" index by setting gap */
> + if (str[i] == ':') {
> + gap = index;
> + gap_count++;
> + i++;
> + }
> + if (gap_count > 1) {
> + parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP,
> + pos + s);
> + goto err_free;
> + }
> + break;
> + default:
> + if (sscanf(&str[i], "%hx", &tmp_v6addr[index]) != 1) {
> + parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP,
> + pos + s);
> + goto err_free;
> + }
> + index++;
> + while (isalnum(str[i]))
> + i++;
> + break;
> + }
> + }
There appears to be no limit to the above loop. I panic'd my machine with:
# echo 'saddr_v6 == 0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef:0123:4567:89ab:cdef' > /sys/kernel/tracing/events/sock/inet_sk_error_report/filter
-- Steve
> + /* The gap_size here represents the number of u16s the "::"
> + * represents; for ::1 the gap size is 7, for feed::face
> + * it is 6, etc.
> + */
> + gap_size = 8 - index;
> + index = 0;
> + for (j = 0; j < 8; ) {
> + if (gap_size > 0 && j == gap) {
> + j += gap_size;
> + } else {
> +#ifdef __BIG_ENDIAN
> + v6addr[j++] = tmp_v6addr[index];
> +#else
> + v6addr[j++] = ((tmp_v6addr[index] & 0xff) << 8) +
> + ((tmp_v6addr[index] & 0xff00) >> 8);
> +#endif
> + index++;
> + }
> + }
> + pred_val = kzalloc(field->size, GFP_KERNEL);
> + memcpy(pred_val, v6addr, field->size);
> + pred->val = (u64)pred_val;
> + pred->fn_num = FILTER_PRED_FN_MEMCMP;
> + if (pred->op == OP_NE)
> + pred->not = 1;
> +
> } else if (str[i] == '0' && tolower(str[i + 1]) == 'x' &&
> field->size > 8) {
> /* For sizes > 8 bytes, we store hex bytes for comparison;
