linux-kernel - [PATCH v2 tracing 3/6] tracing: support IPv6 filter predicates

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Date:   Fri, 28 Apr 2023 16:34:46 +0100
From:   Alan Maguire <alan.maguire@...cle.com>
To:     rostedt@...dmis.org, mhiramat@...nel.org
Cc:     corbet@....net, shuah@...nel.org,
        linux-trace-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alan Maguire <alan.maguire@...cle.com>
Subject: [PATCH v2 tracing 3/6] tracing: support IPv6 filter predicates

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@...cle.com>
---
 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;
+			}
+		}
+		/* 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;
-- 
2.31.1