[PATCH] vsprintf: automatic parameters for %pIS via 'a'

["Jason A. Donenfeld" <Jason@zx2c4.com>]

This patch adds a variable 'a' which indicates that the 'p',
'f', and 's' options should active depending on whether
or not those parameters are actually valid inside the
passed sockaddr.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 Documentation/printk-formats.txt |  7 +++++--
 lib/test_printf.c                | 23 +++++++++++++++++++++++
 lib/vsprintf.c                   | 19 +++++++++++++++++--
 3 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 5d1128b..5c45db4 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -193,7 +193,7 @@ IPv4/IPv6 addresses (generic, with port, flowinfo, scope):
 	%piS	001.002.003.004	or 00010002000300040005000600070008
 	%pISc	1.2.3.4		or 1:2:3:4:5:6:7:8
 	%pISpc	1.2.3.4:12345	or [1:2:3:4:5:6:7:8]:12345
-	%p[Ii]S[pfschnbl]
+	%p[Ii]S[pfsachnbl]
 
 	For printing an IP address without the need to distinguish whether it's
 	of type AF_INET or AF_INET6, a pointer to a valid 'struct sockaddr',
@@ -201,7 +201,10 @@ IPv4/IPv6 addresses (generic, with port, flowinfo, scope):
 
 	The additional 'p', 'f', and 's' specifiers are used to specify port
 	(IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ':' prefix,
-	flowinfo a '/' and scope a '%', each followed by the actual value.
+	flowinfo a '/' and scope a '%', each followed by the actual value. If 'a'
+	is given, 'p', 'f', and 's', when also specified, are only printed
+	depending on whether or not the socketaddr has a non-zero port,
+	flowinfo, and scope.
 
 	In case of an IPv6 address the compressed IPv6 address as described by
 	http://tools.ietf.org/html/rfc5952 is being used if the additional
diff --git a/lib/test_printf.c b/lib/test_printf.c
index 4f6ae60..c3f975e 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -16,6 +16,7 @@
 #include <linux/dcache.h>
 #include <linux/socket.h>
 #include <linux/in.h>
+#include <linux/in6.h>
 
 #define BUF_SIZE 256
 #define PAD_SIZE 16
@@ -301,11 +302,33 @@ ip4(void)
 	test("127.000.000.001|127.0.0.1", "%piS|%pIS", &sa, &sa);
 	sa.sin_addr.s_addr = cpu_to_be32(0x01020304);
 	test("001.002.003.004:12345|1.2.3.4:12345", "%piSp|%pISp", &sa, &sa);
+	test("1.2.3.4:12345", "%pISpa", &sa);
+	test("1.2.3.4", "%pISa", &sa);
+	sa.sin_port = 0;
+	test("1.2.3.4", "%pISpa", &sa);
 }
 
 static void __init
 ip6(void)
 {
+	struct sockaddr_in6 sa = { 0 };
+
+	sa.sin6_family = AF_INET6;
+	sa.sin6_port = cpu_to_be16(12345);
+	sa.sin6_addr.in6_u.u6_addr16[0] = cpu_to_be16(0xabcd);
+	sa.sin6_addr.in6_u.u6_addr16[7] = cpu_to_be16(0x1234);
+	sa.sin6_flowinfo = cpu_to_be32(20);
+	sa.sin6_scope_id = 98;
+
+	test("[abcd::1234]:12345", "%pISpca", &sa);
+	test("[abcd::1234]:12345/20", "%pISpfca", &sa);
+	test("[abcd::1234]:12345/20%98", "%pISpfsca", &sa);
+	sa.sin6_flowinfo = 0;
+	test("[abcd::1234]:12345%98", "%pISpsfca", &sa);
+	sa.sin6_port = 0;
+	test("[abcd::1234]%98", "%pISpfsca", &sa);
+	sa.sin6_scope_id = 0;
+	test("abcd::1234", "%pISpfsca", &sa);
 }
 
 static void __init
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 48ff9c3..80d8ce5 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1145,7 +1145,7 @@ static noinline_for_stack
 char *ip6_addr_string_sa(char *buf, char *end, const struct sockaddr_in6 *sa,
 			 struct printf_spec spec, const char *fmt)
 {
-	bool have_p = false, have_s = false, have_f = false, have_c = false;
+	bool have_p = false, have_s = false, have_f = false, have_c = false, have_a = false;
 	char ip6_addr[sizeof("[xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:255.255.255.255]") +
 		      sizeof(":12345") + sizeof("/123456789") +
 		      sizeof("%1234567890")];
@@ -1169,9 +1169,18 @@ char *ip6_addr_string_sa(char *buf, char *end, const struct sockaddr_in6 *sa,
 		case 'c':
 			have_c = true;
 			break;
+		case 'a':
+			have_a = true;
+			break;
 		}
 	}
 
+	if (have_a) {
+		have_p = have_p && sa->sin6_port;
+		have_s = have_s && sa->sin6_scope_id;
+		have_f = have_f && (sa->sin6_flowinfo & IPV6_FLOWINFO_MASK);
+	}
+
 	if (have_p || have_s || have_f) {
 		*p = '[';
 		off = 1;
@@ -1207,7 +1216,7 @@ static noinline_for_stack
 char *ip4_addr_string_sa(char *buf, char *end, const struct sockaddr_in *sa,
 			 struct printf_spec spec, const char *fmt)
 {
-	bool have_p = false;
+	bool have_p = false, have_a = false;
 	char *p, ip4_addr[sizeof("255.255.255.255") + sizeof(":12345")];
 	char *pend = ip4_addr + sizeof(ip4_addr);
 	const u8 *addr = (const u8 *) &sa->sin_addr.s_addr;
@@ -1225,9 +1234,15 @@ char *ip4_addr_string_sa(char *buf, char *end, const struct sockaddr_in *sa,
 		case 'b':
 			fmt4[2] = *fmt;
 			break;
+		case 'a':
+			have_a = true;
+			break;
 		}
 	}
 
+	if (have_a)
+		have_p = have_p && sa->sin_port;
+
 	p = ip4_string(ip4_addr, addr, fmt4);
 	if (have_p) {
 		*p++ = ':';
-- 
2.7.0