Const'ify variables to make it clear we're not writing to the mbuf data.

Reviewed by:	julian, brian
MFC after:	1 week

5 files changed, 53 insertions, 49 deletions

diff --git a/sys/netgraph/ng_lmi.c b/sys/netgraph/ng_lmi.c
index 4521d74..87f3567 100644
--- a/sys/netgraph/ng_lmi.c
+++ b/sys/netgraph/ng_lmi.c
@@ -556,7 +556,7 @@ static int
 nglmi_rcvdata(hook_p hook, item_p item)
 {
 	sc_p    sc = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
-	u_char *data;
+	const	u_char *data;
 	unsigned short dlci;
 	u_short packetlen;
 	int     resptype_seen = 0;
@@ -584,7 +584,7 @@ nglmi_rcvdata(hook_p hook, item_p item)
 		return (0);
 
 	/* pass the first 4 bytes (already checked in the nglmi_checkdata()) */
-	data = mtod(m, u_char *);
+	data = mtod(m, const u_char *);
 	STEPBY(4);
 
 	/* Now check if there is a 'locking shift'. This is only seen in
@@ -741,7 +741,7 @@ static int
 nglmi_checkdata(hook_p hook, struct mbuf *m)
 {
 	sc_p    sc = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
-	u_char *data;
+	const	u_char *data;
 	u_short packetlen;
 	unsigned short dlci;
 	u_char  type;
@@ -751,7 +751,7 @@ nglmi_checkdata(hook_p hook, struct mbuf *m)
 	int     highest_dlci = 0;
 
 	packetlen = m->m_hdr.mh_len;
-	data = mtod(m, u_char *);
+	data = mtod(m, const u_char *);
 	if (*data != 0x03) {
 		log(LOG_WARNING, "nglmi: unexpected value in LMI(%d)\n", 1);
 		goto reject;
@@ -994,7 +994,7 @@ print:
 		int     i, j, k, pos;
 		char    buf[100];
 		int     loc;
-		u_char *bp = mtod(m, u_char *);
+		const	u_char *bp = mtod(m, const u_char *);
 
 		k = i = 0;
 		loc = (m->m_hdr.mh_len - packetlen);
@@ -1021,7 +1021,7 @@ reject:
 		int     i, j, k, pos;
 		char    buf[100];
 		int     loc;
-		u_char *bp = mtod(m, u_char *);
+		const	u_char *bp = mtod(m, const u_char *);
 
 		k = i = 0;
 		loc = (m->m_hdr.mh_len - packetlen);
diff --git a/sys/netgraph/ng_pppoe.c b/sys/netgraph/ng_pppoe.c
index 7c26cdc..3832d84 100644
--- a/sys/netgraph/ng_pppoe.c
+++ b/sys/netgraph/ng_pppoe.c
@@ -202,7 +202,7 @@ struct sess_neg {
 	struct callout_handle	timeout_handle;   /* see timeout(9) */
 	u_int			timeout; /* 0,1,2,4,8,16 etc. seconds */
 	u_int			numtags;
-	struct pppoe_tag	*tags[NUMTAGS];
+	const struct pppoe_tag	*tags[NUMTAGS];
 	u_int			service_len;
 	u_int			ac_name_len;
 
@@ -277,7 +277,8 @@ union uniq {
 static void	pppoe_start(sessp sp);
 static void	sendpacket(sessp sp);
 static void	pppoe_ticker(void *arg);
-static struct pppoe_tag* scan_tags(sessp	sp, struct pppoe_hdr* ph);
+static const	struct pppoe_tag *scan_tags(sessp sp,
+			const struct pppoe_hdr* ph);
 static	int	pppoe_send_event(sessp sp, enum cmd cmdid);
 
 /*************************************************************************
@@ -328,10 +329,11 @@ restart:
 /*
  * Return the location where the next tag can be put 
  */
-static __inline struct pppoe_tag*
-next_tag(struct pppoe_hdr* ph)
+static __inline const struct pppoe_tag*
+next_tag(const struct pppoe_hdr* ph)
 {
-	return (struct pppoe_tag*)(((char*)&ph->tag[0]) + ntohs(ph->length));
+	return (const struct pppoe_tag*)(((const char*)&ph->tag[0])
+	    + ntohs(ph->length));
 }
 
 /*
@@ -339,28 +341,28 @@ next_tag(struct pppoe_hdr* ph)
  * Don't trust any length the other end says.
  * but assume we already sanity checked ph->length.
  */
-static struct pppoe_tag*
-get_tag(struct pppoe_hdr* ph, u_int16_t idx)
+static const struct pppoe_tag*
+get_tag(const struct pppoe_hdr* ph, u_int16_t idx)
 {
-	char *end = (char *)next_tag(ph);
-	char *ptn;
-	struct pppoe_tag *pt = &ph->tag[0];
+	const char *const end = (const char *)next_tag(ph);
+	const char *ptn;
+	const struct pppoe_tag *pt = &ph->tag[0];
 	/*
 	 * Keep processing tags while a tag header will still fit.
 	 */
 AAA
-	while((char*)(pt + 1) <= end) {
+	while((const char*)(pt + 1) <= end) {
 	    /*
 	     * If the tag data would go past the end of the packet, abort.
 	     */
-	    ptn = (((char *)(pt + 1)) + ntohs(pt->tag_len));
+	    ptn = (((const char *)(pt + 1)) + ntohs(pt->tag_len));
 	    if(ptn > end)
 		return NULL;
 
 	    if(pt->tag_type == idx)
 		return pt;
 
-	    pt = (struct pppoe_tag*)ptn;
+	    pt = (const struct pppoe_tag*)ptn;
 	}
 	return NULL;
 }
@@ -383,7 +385,7 @@ AAA
 }
 
 static void
-insert_tag(sessp sp, struct pppoe_tag *tp)
+insert_tag(sessp sp, const struct pppoe_tag *tp)
 {
 	int	i;
 	negp neg;
@@ -412,7 +414,7 @@ AAA
 static void
 make_packet(sessp sp) {
 	struct pppoe_full_hdr *wh = &sp->neg->pkt->pkt_header;
-	struct pppoe_tag **tag;
+	const struct pppoe_tag **tag;
 	char *dp;
 	int count;
 	int tlen;
@@ -432,7 +434,7 @@ AAA
 			sp->neg->numtags = count;
 			break;	/* XXX chop off what's too long */
 		}
-		bcopy((char *)*tag, (char *)dp, tlen);
+		bcopy(*tag, (char *)dp, tlen);
 		length += tlen;
 		dp += tlen;
 	}
@@ -456,7 +458,7 @@ AAA
 #define NG_MATCH_ANY	2
 
 static hook_p
-pppoe_match_svc(node_p node, char *svc_name, int svc_len, int match)
+pppoe_match_svc(node_p node, const char *svc_name, int svc_len, int match)
 {
 	sessp	sp	= NULL;
 	negp	neg	= NULL;
@@ -503,7 +505,7 @@ AAA
  * Routine to find a particular session that matches an incoming packet	  *
  **************************************************************************/
 static hook_p
-pppoe_findsession(node_p node, struct pppoe_full_hdr *wh)
+pppoe_findsession(node_p node, const struct pppoe_full_hdr *wh)
 {
 	sessp	sp = NULL;
 	hook_p hook = NULL;
@@ -534,7 +536,7 @@ AAA
 }
 
 static hook_p
-pppoe_finduniq(node_p node, struct pppoe_tag *tag)
+pppoe_finduniq(node_p node, const struct pppoe_tag *tag)
 {
 	hook_p hook = NULL;
 	priv_p	privp = NG_NODE_PRIVATE(node);
@@ -889,7 +891,7 @@ AAA
 }
 
 static int
-send_acname(sessp sp, struct pppoe_tag *tag)
+send_acname(sessp sp, const struct pppoe_tag *tag)
 {
 	int error;
 	struct ng_mesg *msg;
@@ -936,13 +938,13 @@ ng_pppoe_rcvdata(hook_p hook, item_p item)
 	node_p			node = NG_HOOK_NODE(hook);
 	const priv_p		privp = NG_NODE_PRIVATE(node);
 	sessp			sp = NG_HOOK_PRIVATE(hook);
-	struct pppoe_full_hdr	*wh;
-	struct pppoe_hdr	*ph;
+	const struct pppoe_full_hdr *wh;
+	const struct pppoe_hdr	*ph;
 	int			error = 0;
 	u_int16_t		session;
 	u_int16_t		length;
 	u_int8_t		code;
-	struct pppoe_tag	*utag = NULL, *tag = NULL;
+	const struct pppoe_tag	*utag = NULL, *tag = NULL;
 	hook_p 			sendhook;
 	struct {
 		struct pppoe_tag hdr;
@@ -1681,21 +1683,21 @@ AAA
  * output packet. Don't do any tags that have been handled in the main
  * state machine.
  */
-static struct pppoe_tag* 
-scan_tags(sessp	sp, struct pppoe_hdr* ph)
+static const struct pppoe_tag* 
+scan_tags(sessp	sp, const struct pppoe_hdr* ph)
 {
-	char *end = (char *)next_tag(ph);
-	char *ptn;
-	struct pppoe_tag *pt = &ph->tag[0];
+	const char *const end = (const char *)next_tag(ph);
+	const char *ptn;
+	const struct pppoe_tag *pt = &ph->tag[0];
 	/*
 	 * Keep processing tags while a tag header will still fit.
 	 */
 AAA
-	while((char*)(pt + 1) <= end) {
+	while((const char*)(pt + 1) <= end) {
 		/*
 		 * If the tag data would go past the end of the packet, abort.
 		 */
-		ptn = (((char *)(pt + 1)) + ntohs(pt->tag_len));
+		ptn = (((const char *)(pt + 1)) + ntohs(pt->tag_len));
 		if(ptn > end)
 			return NULL;
 
@@ -1715,7 +1717,7 @@ AAA
 		case	PTT_GEN_ERR:
 			break;
 		}
-		pt = (struct pppoe_tag*)ptn;
+		pt = (const struct pppoe_tag*)ptn;
 	}
 	return NULL;
 }
diff --git a/sys/netgraph/ng_pptpgre.c b/sys/netgraph/ng_pptpgre.c
index 1799ad0..d760ed8 100644
--- a/sys/netgraph/ng_pptpgre.c
+++ b/sys/netgraph/ng_pptpgre.c
@@ -569,8 +569,8 @@ ng_pptpgre_recv(node_p node, item_p item)
 {
 	const priv_p priv = NG_NODE_PRIVATE(node);
 	int iphlen, grelen, extralen;
-	struct greheader *gre;
-	struct ip *ip;
+	const struct greheader *gre;
+	const struct ip *ip;
 	int error = 0;
 	struct mbuf *m;
 
@@ -595,7 +595,7 @@ bad:
 		NG_FREE_ITEM(item);
 		return (ENOBUFS);
 	}
-	ip = mtod(m, struct ip *);
+	ip = mtod(m, const struct ip *);
 	iphlen = ip->ip_hl << 2;
 	if (m->m_len < iphlen + sizeof(*gre)) {
 		if ((m = m_pullup(m, iphlen + sizeof(*gre))) == NULL) {
@@ -603,9 +603,9 @@ bad:
 			NG_FREE_ITEM(item);
 			return (ENOBUFS);
 		}
-		ip = mtod(m, struct ip *);
+		ip = mtod(m, const struct ip *);
 	}
-	gre = (struct greheader *)((u_char *)ip + iphlen);
+	gre = (const struct greheader *)((const u_char *)ip + iphlen);
 	grelen = sizeof(*gre) + sizeof(u_int32_t) * (gre->hasSeq + gre->hasAck);
 	if (m->m_pkthdr.len < iphlen + grelen) {
 		priv->stats.recvRunts++;
@@ -617,8 +617,8 @@ bad:
 			NG_FREE_ITEM(item);
 			return (ENOBUFS);
 		}
-		ip = mtod(m, struct ip *);
-		gre = (struct greheader *)((u_char *)ip + iphlen);
+		ip = mtod(m, const struct ip *);
+		gre = (const struct greheader *)((const u_char *)ip + iphlen);
 	}
 
 	/* Sanity check packet length and GRE header bits */
@@ -628,7 +628,8 @@ bad:
 		priv->stats.recvBadGRE++;
 		goto bad;
 	}
-	if ((ntohl(*((u_int32_t *)gre)) & PPTP_INIT_MASK) != PPTP_INIT_VALUE) {
+	if ((ntohl(*((const u_int32_t *)gre)) & PPTP_INIT_MASK)
+	    != PPTP_INIT_VALUE) {
 		priv->stats.recvBadGRE++;
 		goto bad;
 	}
diff --git a/sys/netgraph/ng_rfc1490.c b/sys/netgraph/ng_rfc1490.c
index ec1fc19..778d07b 100644
--- a/sys/netgraph/ng_rfc1490.c
+++ b/sys/netgraph/ng_rfc1490.c
@@ -215,12 +215,13 @@ ng_rfc1490_rcvdata(hook_p hook, item_p item)
 
 	NGI_GET_M(item, m);
 	if (hook == priv->downlink) {
-		u_char *start, *ptr;
+		const u_char *start;
+		const u_char *ptr;
 
 		if (!m || (m->m_len < MAX_ENCAPS_HDR
 		    && !(m = m_pullup(m, MAX_ENCAPS_HDR))))
 			ERROUT(ENOBUFS);
-		ptr = start = mtod(m, u_char *);
+		ptr = start = mtod(m, const u_char *);
 
 		/* Must be UI frame */
 		if (*ptr++ != HDLC_UI)
@@ -237,7 +238,7 @@ ng_rfc1490_rcvdata(hook_p hook, item_p item)
 				u_int16_t etype;
 
 				ptr += 3;
-				etype = ntohs(*((u_int16_t *) ptr));
+				etype = ntohs(*((const u_int16_t *)ptr));
 				ptr += 2;
 				m_adj(m, ptr - start);
 				switch (etype) {
diff --git a/sys/netgraph/ng_socket.c b/sys/netgraph/ng_socket.c
index 09d1c46..43475ef 100644
--- a/sys/netgraph/ng_socket.c
+++ b/sys/netgraph/ng_socket.c
@@ -571,7 +571,7 @@ ng_detach_common(struct ngpcb *pcbp, int which)
 static int
 ng_internalize(struct mbuf *control, struct thread *td)
 {
-	struct cmsghdr *cm = mtod(control, struct cmsghdr *);
+	const struct cmsghdr *cm = mtod(control, const struct cmsghdr *);
 	struct file *fp;
 	struct vnode *vn;
 	int oldfds;